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• Experimentally characterized the interfacial stress gradients with features of a maximum value below 0.4 MPa/μm and a constant range width of 35 μm in the Ti layer of Ti/Al layered metal. • The interfacial stress gradients were neither generated by the ti layer itself nor had a significant effect on the deformation of the Ti layer. • The incompatible deformation between Ti and Al layer is the origin of the interfacial stress gradient. As one of the heterostructures, the layered structure has attracted extensive research interest as it achieves superior properties to individual components. The layer interface is considered a critical factor in determining the mechanical properties of layered metals, where heterogeneity across the interface results in the strengthening of the soft layer and forming an interfacial stress gradient in the hard layer. However, there is still limited research associated with the formation of interfacial stress gradients in the hard layer, as stress measurement at high spatial resolution remains technically challenging. In the present study, we experimentally quantified the formation of interfacial stress gradients in the Ti layer of Ti/Al layered metal upon tension using in-situ high-energy X-ray diffraction (XRD). The analysis coupling in-situ high-energy XRD and in-situ electron back-scattered diffraction (EBSD) suggested that the interfacial stress gradient in the Ti layer rapidly rose as the Al layer was insufficient to accommodate the deformation of Ti. During the later deformation stage, collective effects of dislocation motion and geometrically necessary dislocation (GND) accumulation in the Al layer determined the evolution of interfacial stress gradients. The maximum interfacial stress gradient is below 0.4 MPa/μm in Ti layers, with a constant range width of 35 μm independent of the macroscopic strain. The present study therefore opens a new window to local stress modification using incompatible component deformation, which is instructive for the design and fabrication of high-performance layered metals. [Display omitted] [ABSTRACT FROM AUTHOR]

• Al-Mg-Sc-Zr components fabricated by WAAM were nearly full dense. • Unique microstructure features of WAAM-processed Al-Mg-Sc-Zr. • The short-circuit transition mode of CMT and microalloying effect of Sc + Zr change the microstructure morphologies of molten pool. • Controlling interlayer temperature at 100 °C improved the strength. • Solid solution strengthening was the main strengthening mechanism. Wire arc additive manufacturing (WAAM) technique is a promising approach to producing large-scale metal components due to high deposition efficiency and low production cost. However, fundamental research about WAAM-processed Al-Mg-Sc-Zr alloy was still fewer. In this study, Al-6.54Mg-0.36Sc-0.11Zr (wt%) components were successfully manufactured by WAAM with an interlayer temperature at 100 °C (named IW) and continuous printing (named CP), and the corresponding porosity, microstructure, and mechanical properties of components were studied in detail. The porosity of components as-deposited was relatively low, about 0.385% and 0.116%, respectively. The microstructures of the two components exhibited the same distribution characteristics in XZ and YZ planes: fine equiaxed grains (FEG) at remelted zone + FEG and coarse equiaxed grain (CEG) alternative distribution at middle zone + FEG at the top zone of the molten pool. The average grain size of component IW was about 10.51 ± 6.01 μm, and that of component CP significantly increased, to about 11.85 ± 5.86 μm. The short-circuit transition mode of cold metal transfer technology and the heterogeneous nucleation effect of primary Al 3 (Sc, Zr) and Al 3 (Sc, Zr, Ti) phases together promoted the formation of equiaxed grains and refined the microstructures. After heat treatment at 325 °C and 6 h, nano-Al 3 Sc precipitated with a size of about 15–50 nm. The yield strength (YS) of components IW and CP increased from 171 ± 3 to 261 ± 1 MPa and 168 ± 7 to 240 ± 17 MPa, respectively. Component IW had the highest ultimate tensile strength, about 400 ± 1 MPa. For WAAM-processed Al-Mg-Sc-Zr alloys, the contribution of the strengthening mechanism to YS was solid solution strengthening > precipitation strengthening > fine grain strengthening > dislocation strengthening. [Display omitted] [ABSTRACT FROM AUTHOR]

• A double-peak age hardening is observed in the LPBF-processed Al-5Mg-2Si-3 Zn alloy. • β″ and η′ phases are sequentially precipitated in the peak aged states. • The hierarchical structures co-contribute to the high strength of alloy. Laser powder bed fusion (LPBF) with a high cooling rate delivers a huge potential in improving the solid solubility limit and subsequent precipitation strengthening. In this work, a double-peak age hardening was observed in the LPBF-processed Al-5Mg-2Si-3Zn alloy, in which the higher hardness value was 176 HV for the second peak and the lower hardness was 169 HV for the first peak. The yield strength was remarkably enhanced from the 349 MPa under as-built condition to the 434 MPa under as-aged condition. It was found that the double peak hardening was highly associated with Zn alloying, which promoted the formation of Zn segregation with overlapping of nanoscale eutectic Mg 2 Si cells in the as-built state. The aged microstructures were characterized by the uniformly distributed Zn solute and the precipitation of the secondary lath-shaped β″ phase, which is responsible for the first peak age strengthening. Further, the pre-existed β″ in conjunction with the newly formed needle-shaped (Mg, Zn)-rich Guinier-Preston (GP) zone and plate-shaped η′ precipitates co-contribute to the strengthening in the second peak. The synergistic strengthening of multiple precipitates is very effective and efficient for the development of additively manufactured aluminium alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

• By manipulating the cold-welding of composite powders during the segmented ball milling, two-level heterogeneity in microstructures including MgO-rich FG regions and heterogeneous lamellar structure composed of band-like CG regions embedded within FG regions were successfully developed, which exacerbates the mechanical property mismatch among distinct domains and consequently contributes to high HDI strengthening. • The absence of movable dislocations in the FG region necessitates higher stress for yielding, which is responsible for the "yield drop" of the bulk composite. During the subsequent deformation process, the significant interaction between MgO and dislocations within the FG regions maintains sustainable strain hardening. • The initial deformation of the CGs results in the accumulation of high strain, leading to the formation of dislocation walls that facilitates the aggregation and recovery of dislocations. This process promotes the transformation of CGs into primary equiaxed grains or substructures in the subsequent strain deformation, thereby significantly contributing to the work hardening. Constructing heterostructures is essential for tailoring the mechanical properties of Al matrix composites (AMCs). In this work, multi-level heterostructures were achieved in AMCs by manipulating the cold welding of initial composite powders and in-situ solid-state reaction. The resulting microstructure features band-like coarse grain (CG) regions embedded within fine grain (FG) regions, demonstrating a heterogeneous lamella (HL) grain structure. Moreover, the in-situ solid-state reaction between Al, Mg and CuO gives rise to the generation of intragranular nano-sized MgO particles, which are primarily distributed in FGs. This unique microstructure activates hetero-deformation induced (HDI) strengthening by exacerbating the mechanical property mismatch between distinct domains. Notably, the FG regions necessitate high stress for activating dislocations, causing a "yield drop" in the bulk composite. It was also elucidated that CGs experience higher stress in the early stages of deformation compared to FG domains, leading to the formation of dislocation walls. The aggregation and recovery of these dislocations facilitate the transformation of CGs into primary equiaxed grains or substructures during subsequent plastic deformation, thereby contributing to the exceptional strain hardening of the composite. Furthermore, the intragranular distribution of MgO reinforcement promotes significant dislocation proliferation and achieves stress redistribution, which rationalizes the considerable ductility of the composite. This work offers insights into the achievement of multi-level heterogeneous composites with superior mechanical properties by synergistically regulating grain structure and reinforcement distribution configuration. [Display omitted] [ABSTRACT FROM AUTHOR]

• (MoNbTaTiZr) 1- x N x high-entropy nitride (HEN) coatings with different nitrogen contents were fabricated by magnetron sputtering. • Increasing nitrogen content caused the structural transformation in coating from pure BCC phases to nanocomposites and then to FCC polycrystalline. • (MoNbTaTiZr) 0.83 N 0.17 coating exhibited the highest hardness of 32.4 ± 2.6 GPa and H / E ratio at 0.09, together with the strongest corrosion resistance. • Densely nanocomposites with refined nanograins embedded into amorphous matrix contributed outstanding properties of (MoNbTaTiZr) 0.83 N 0.17 coating. High-entropy materials possess high hardness and strong wear resistance, yet the key bottleneck for their practical applications is the poor corrosion resistance in harsh environments. In this work, the high-entropy nitride (HEN) coatings of (MoNbTaTiZr) 1- x N x (x = 0–0.47) were fabricated using a hybrid direct current magnetron sputtering technique. The research focus was dedicated to the effect of nitrogen content on the microstructure, mechanical and electrochemical properties. The results showed that the as-deposited coatings exhibited a typical body-centered cubic (BCC) structure without nitrogen, while the amorphous matrix with face-centered cubic (FCC) nanocrystalline grain was observed at x = 0.17. Further increasing x in the range of 0.35–0.47 caused the appearance of polycrystalline FCC phase in structure. Compared with the MoNbTaTiZr metallic coating, the coating containing nitrogen favored the high hardness around 13.7–32.4 GPa, accompanied by excellent tolerance both against elastic and plastic deformation. Furthermore, such N-containing coatings yielded a low corrosion current density of about 10−8–10−7 A/cm2 and high electrochemical impedance of 106 Ω cm2 in 3.5 wt.% NaCl solution, indicating the superior corrosion resistance. The reason for the enhanced electrochemical behavior could be ascribed to the spontaneous formation of protective passive layers over the coating surface, which consisted of the dominated multi-elemental oxides in chemical stability. Particularly, noted that the (MoNbTaTiZr) 0.83 N 0.17 coating displayed the highest hardness of 32.4 ± 2.6 GPa and H/E ratio at 0.09, together with remarkable corrosion resistance, proposing the strongest capability for harsh-environmental applications required both good anti-wear and anti-corrosion performance. [Display omitted] [ABSTRACT FROM AUTHOR]

• The GFA, thermal and mechanical properties of Zr 70–75 (Al, Ni, Cu, Ag) 25–30 were studied. • Annealing-induced precipitated quasicrystal phase in 75 %Zr glassy ribbon. • Annealed ribbons with quasicrystal precipitations show good bending plasticity. • The as-spun and annealed ribbons exhibit high strength above 1200 MPa and plastic strain > 0.4 %. A glassy (G) phase was formed for Zr-rich Zr 70–75 (Al, Ni, Cu, Ag) 25–30 (atomic percent, at.%) melt-spun alloy ribbons. These glassy alloys exhibit the glass transition, followed by a supercooled liquid region and then three-stage crystallization. The glass transition temperature and the onset temperature for the first-stage crystallization (T x1) decrease from 630 to 668 K, respectively for the 70Zr alloy to 619 and 652 K, respectively for the 75Zr alloy. The first-stage exothermic peak is due to the precipitation of an icosahedral quasicrystal (IQ) phase. The IQ particle size decreases from 10 nm to 6 nm with increasing Zr content from 70 at.% to 74 at.%. The [ G + IQ] phases change to Zr 2 Ni + Zr 2 (Cu, Ag) phases after the second exothermic peak and then Zr 2 Ni + Zr 2 (Cu, Ag) + Zr 5 Al 3 phases after the third stage. It is noticed that the as-spun glassy alloy ribbons as well as the annealed [ G + IQ] phase ribbons exhibit good bending plasticity. Furthermore, the 70Zr thicker ribbons also exhibit high tensile fracture strength of 1090–1187 MPa and plastic elongation of 0.17 %–0.42 %. The fracture mode is similar to that of ordinary bulk metallic glasses. The Vickers hardness (H v) is 480 for 70Zr alloy and decreases to 436 for 75Zr alloy. The precipitation of IQ phase causes a significant increase in H v to about 554. The formations of glassy alloys with high Zr contents of 70 at.%–75 at.% by melt spinning as well as the [ G + IQ] phase alloys with good bending plasticity by annealing hold promise for the creation of a new type of engineering material, transcending mere academic novelty. [Display omitted] [ABSTRACT FROM AUTHOR]

• An oxide-dispersion-strengthened Fe-Cr-Al alloy with a bimodal grain size distribution is fabricated. • The heterogeneous microstructure improves the strength and ductility of Fe-Cr-Al alloy simultaneously. • Through selecting appropriate powder size and sintering processes, the microstructure of Fe-Cr-Al alloy towards a heterogeneous grain size distribution can be tailored. An oxide-dispersion-strengthened (ODS) Fe-10Cr-6.1Al-0.3Zr-0.1Y alloy with a bimodal grain size distribution was developed via a simple process of internal oxidation and powder forging. The intentionally promoted heterogeneous microstructure consists of coarse-grained "core" regions enclosed by mutually connected fine-grained "shell" zones, facilitated by unevenly distributed oxide particles. The sample sintered and then forged at 1150 °C exhibited a yield strength of 598 MPa, a tensile strength of 734 MPa, and a fracture elongation of 25.1 %. Such simultaneously enhanced strength and ductility are significantly above those of cast or previous powder-consolidated counterparts. During tensile deformation, a strain gradient is built up across the inhomogeneous grains and a high density of geometrically necessary dislocations was observed near the interfaces of matrix/oxide particles, both contributing to heterogeneous deformation-induced strengthening. This elevates the work hardening rate and consequently the tensile elongation. Quantitative analysis indicates that the dislocation build-up during forging makes the dominant contribution to the high yield strength of Ox-1150. The present study offers a new route to the preparation of heterogeneously structured ODS Fe-Cr-Al alloys and provides guidance for optimizing the mechanical properties of such alloys in terms of strength-ductility synergy. [Display omitted] [ABSTRACT FROM AUTHOR]

• Unalloyed Zn and Zn-2Cu alloys were successfully prepared using the L -PBF technique. • The 2 wt.% additions of Cu increased the UTS of Zn, and the Zn-2Cu alloy had faster corrosion rates than unalloyed Zn. • As Ev increases, a progressively lower UTS is exhibited for unalloyed Zn and Zn-2Cu alloys, respectively. • A correlation mechanism between microstructure, mechanical properties, and corrosion behavior was obtained. Additively manufactured (AM) biodegradable zinc (Zn) alloys constitute an important branch of orthopedic implants because of their moderate degradation properties and bone-mimicking mechanical properties. In this paper, the microstructural evolution and corrosion mechanisms of zinc-copper (Zn-Cu) alloys prepared by the laser-powder-bed-fusion (L-PBF) additive manufacturing method were investigated. Alloying with Cu significantly increases the ultimate tensile strength (UTS) of unalloyed Zn, but the UTS and ductility of unalloyed Zn and Zn-2Cu decrease with increasing laser energy density. Unalloyed Zn has a dendritic microstructure, while Zn-2Cu alloy has a peritectic microstructure. The formation of round peritectic grains is due to the low-temperature gradient of unalloyed Zn during the AM. The Zn-2Cu samples exhibited higher corrosion rates, addressing the problem of slow degradation of unalloyed Zn. The grain size distribution influences the corrosion behavior of the material. It enhances the corrosion rates of materials with fine grains in a non-passivating environment. However, the 100% extracts of Zn-2Cu samples exhibited greater values of cellular activity compared to unalloyed Zn samples, thus confirming their better cytocompatibility. This work demonstrates the great potential to design and modulate biodegradable Zn alloys to fulfill clinical needs by using AM technology. [Display omitted] [ABSTRACT FROM AUTHOR]

• Extended solid solution (20 at.% solute) was fabricated for typical immiscible Cu-Fe alloy in bulk state by high pressure torsion. • Phase decomposition and the relationship between microstructure and mechanical properties in extended solid solution of immiscible system were comprehensively investigated for the first time. • Two kinds of Fe phases, including the α -Fe grains (16–261 nm) at the Cu grain boundaries and the γ -Fe particles (4–10 nm) in the Cu grain interior, were identified in the annealed specimens. • The change from spinodal decomposition to classical nucleation-growth mode with decreasing Fe content near grain boundaries was observed. • The contributions of different strengthening mechanisms were quantitatively evaluated. Grain boundary hardening of Cu and precipitation hardening of γ -Fe in Cu grains were revealed to play a major role (80%–90%) in strengthening the decomposed Cu-Fe nanocomposites. Extended solid solution of immiscible systems, achieved by extreme processing approaches, can be transformed into nanostructured composites via phase decomposition, which are drawing great research attention for their excellent thermal stability and high strength. Here we fabricated the supersaturated solid solution of Cu-20 at.%Fe, a typical immiscible alloy, in bulk state by high pressure torsion, which provides a great freedom over powders for studying the microstructure evolution and mechanical properties in the process of the phase decomposition in immiscible alloys. We found that in the Cu-Fe solid solution, spinodal decomposition of the Fe phases took place at the initial stage of annealing through volume diffusion. This process gives rise to: (1) metastable γ -Fe particles in the Cu grains with coherent Fe/Cu interface, and (2) the more stable α -Fe phase at the grain boundaries. This process was accompanied by moving boundary reaction which first proceeded in the pattern of spinodal decomposition and then changed into classical nucleation-growth mode with the depletion of Fe atoms in Cu. The resultant Cu-Fe nanocomposites were jointly strengthened by the ultrafine Cu and α -Fe grains according to the rule of mixture, including grain boundary strengthening and the hardening of nanoscale γ -Fe precipitates in the Cu grains. The effects of different strengthening mechanisms were scrutinized and their contributions to mechanical properties were quantitatively evaluated. This work sheds light onto the opportunity of designing and fabricating nanostructured composites via phase decomposition in immiscible systems. [Display omitted] [ABSTRACT FROM AUTHOR]

• Novel Zr63.2Cu36.8 (wt.%) alloys were prepared by the vacuum melting for the brazing of CoCrFeMnNi HEA and Zr alloy. • BCC structural HEAP layer constituted of fine grains formed by in-situ reaction, releasing effectively the residual stress concentrated on it because of its better plasticity. • Micro-nanoscale HCP (Zr,Cu) precipitates could endow brittle layered Zr(Cr,Mn) 2 with FCC structure with the elevated plasticity. • High shear strength of 172.1 MPa (abut 62.6% of Zr-3 yield strength) in HEA/Zr-3 joints brazed at 1010 °C for 10 min was received. In the pursuit of manufacturing intricate components for the nuclear industry, we developed a novel Zr63.2Cu36.8 (wt.%) alloy via vacuum melting for brazing applications involving equiatomic high-entropy alloys (HEA) of CoCrFeMnNi and zircaloy (Zr-3). We systematically investigated the influence of various brazing parameters on microstructure evolution and shear properties. Furthermore, we established a comprehensive understanding of the relationship between the lattice structure of interfacial products, residual stress, and fracture behavior in HEA/Zr-Cu/Zr-3 joints. Our findings revealed that under specific conditions (1010 °C for 10 min), the reaction products in HEA/Zr-Cu/Zr-3 joints consisted of lamellar HEAP/lamellar Zr(Cr,Mn) 2 , granular (Zr,Cu)/Zr 2 (Cu,Ni,Co,Fe), bulk Zr(Cr,Mn) 2 , and Zrss. With increasing temperature and prolonged holding time, the layered HEAP and Zr(Cr,Mn) 2 phases adjacent to the HEA substrates thickened, while the relative amounts of Zr 2 (Cu,Ni,Co,Fe) decreased, with a remarkable increase in ductile Zrss. Growth kinetics analysis of the reaction layer and EBSD analysis indicated that the HEAP phases exhibited a lower growth rate compared to the Zr(Cr,Mn) 2 layer during brazing, and both phases exhibited random grain orientations. Particularly noteworthy was the precipitation of (Zr,Cu) within the layered Zr(Cr,Mn) 2 , which increased and coarsened with higher temperatures and extended durations. Finite element analysis and TEM analysis revealed higher residual stresses at the non-coherent Zr(Cr,Mn) 2 /HEAP interface with a lattice mismatch of 40.6%. The body-centered cubic (BCC) structural HEAP, composed of fine grains, effectively mitigated the concentrated residual stresses due to its superior plasticity. Moreover, micro-nanoscale close-packed hexagonal (HCP) precipitates (Zr,Cu) were distributed within the brittle Zr(Cr,Mn) 2 phases, contributing to the overall strength improvement of the joints. Consequently, high-quality HEA/Zr-3 joints were achieved, featuring a maximum strength of 172.1 MPa, equivalent to approximately 62.6% of the yield strength of Zr-3. These results highlight the potential of Zr63.2Cu36.8 (wt.%) alloys in advanced brazing applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Investigate microstructure's impact on Ti-alloys mechanical properties using mainstream powder-type AM. • Optimize grain size and morphology to tailor Ti alloy strength and unlock dual enhancement of strength and ductility via AM. • Examine macro and micro defects in AM-fabricated Ti alloys and their effects on mechanical behavior. • Address challenges and opportunities, guiding advancements for high-performance Ti alloys via AM. Ti and its alloys have been broadly adopted across various industries owing to their outstanding properties, such as high strength-to-weight ratio, excellent fatigue performance, exceptional corrosion resistance and so on. Additive manufacturing (AM) is a complement to, rather than a replacement for, traditional manufacturing processes. It enhances flexibility in fabricating complex components and resolves machining challenges, resulting in reduced lead times for custom designs. However, owing to distinctions among various AM technologies, Ti alloys fabricated by different AM methods usually present differences in microstructure and defects, which can significantly influence the mechanical performance of built parts. Therefore, having an in-depth knowledge of the scientific aspects of fabrication and material properties is crucial to achieving high-performance Ti alloys through different AM methods. This article reviews the mechanical properties of Ti alloys fabricated by two mainstream powder-type AM techniques: powder bed fusion (PBF) and directed energy deposition (DED). The review examines several key aspects, encompassing phase formation, grain size and morphology, and defects, and provides an in-depth analysis of their influence on the mechanical behaviors of Ti alloys. This review can aid researchers and engineers in selecting appropriate PBF or DED methods and optimizing their process parameters to fabricate high-performance Ti alloys for a wide range of industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• C f /(CrZrHfNbTa)C–SiC high-entropy ceramic matrix composites with excellent load-bearing, electromagnetic shielding and ablation resistance were designed and reported for the first time. • Single-phase (CrZrHfNbTa)C was successfully synthesized at 1700 ℃ with a small amount of Si as an additive, which is the lowest temperature for the synthesis of (CrZrHfNbTa)C via solid-phase route reported in literature. • C f /(CrZrHfNbTa)C–SiC composites were fabricated by a combined processing of SIL and PIP. • The total electromagnetic interference shielding efficiency of the composites are as high as 88.2 dB and 90 dB respectively in X-band and Ku-band. In this work, C f /(CrZrHfNbTa)C–SiC high-entropy ceramic matrix composites with good load-bearing, electromagnetic shielding and ablation resistance were designed and reported for the first time. The composites were fabricated by an efficient combined processing of slurry infiltration lamination (SIL) and precursor infiltration and pyrolysis (PIP). Density and porosity of the as-fabricated composites are 2.72 g/cm3 and 12.44 vol.%, respectively, and the flexural strength is 185 ± 13 MPa. Due to the carbon fiber reinforcement with high conductivity and strong reflection, and high-entropy (CrZrHfNbTa)C ceramic matrix with strong absorbability, the total Electromagnetic interference shielding efficiency (SE T) of the composites with a thickness of 3 mm are as high as 88.2 dB and 90 dB respectively in X-band and Ku-band. This means that higher than 99.999999 % electromagnetic shielding is achieved at 8–18 GHz, showing excellent electromagnetic shielding performance. The C f /(CrZrHfNbTa)C–SiC composites also present excellent ablation resistance, with the linear and mass ablation rates of 0.9 µm/s and 1.82 mg/s after ablation at the heat flux of 5 MW/m2 for 300 s (∼2450 °C). This work opens a new insight for the synergistic design of structural and functional integrated materials with load-bearing, electromagnetic shielding and ablation resistance, etc. [Display omitted] [ABSTRACT FROM AUTHOR]

• Novel Fe-Based high-entropy alloy with excellent mechanical properties was designed. • The microstructural evolution according to different aging routes has been studied. • Heterogeneous microstructure enhanced yield strength and strain-hardening effect. • The property-cost dilemma was resolved via composition and microstructure design. High-entropy alloys (HEAs) consisting of CoCrFeNiAlTi systems, with a face-centered cubic (FCC) matrix reinforced by ordered L1 2 precipitates, have demonstrated exceptional strength-ductility combinations. However, the current compositional design of HEAs heavily relies on high Ni and Co contents, compromising the balance between properties and cost. Thus, it is crucial to optimize the cost-performance trade-off by fine-tuning the range of Fe, Co, and Ni, while maintaining excellent strength-ductility combination. In this study, we propose a novel Fe-based HEA with nanosized precipitates and a heterogeneous grain distribution, achieving a strength-ductility combination comparable to state-of-the-art Ni- or Co-based HEAs. The alloy benefits from both precipitation hardening and hetero-deformation-induced strengthening attributed to the heterogeneous grain distribution, resulting in excellent yield strength of 1433 MPa, tensile strength of 1599 MPa, and ductility of 22%. The microstructural evolution and its influence on mechanical properties are unraveled with respect to the observation of precipitate-dislocation interaction and hetero-deformation-induced stress (HDI stress) evaluation. This study suggests that the challenge of balancing properties and cost can be addressed through optimized compositional and microstructural design. [Display omitted] [ABSTRACT FROM AUTHOR]

• The ideal aging temperature of GK140 is within 225–250 ℃. • The premature fracture mechanism in the GK140 alloy aged at 175–200 ℃ is cleavage cracking caused by the shearing of β' precipitates by basal dislocations. • The size of β' phase formed at 225–250 ℃ is comparatively large, and therefore the formation of cleavage cracks is suppressed. The effect of precipitation aging on the fracture behavior of cast Mg–14.23Gd–0.45Zr (wt.%) alloy at room temperature has been studied in this work. Uniaxial tensile and three-point bending tests were conducted on samples peak-aged at 175, 200, 225, and 250 ℃. Notably, samples aged at 175 ℃ and 200 ℃ exhibited premature fracture during the uniaxial tensile test. Through fractographic observations of the tensile test samples and electron backscattered diffraction (EBSD) analysis on the samples subjected to three-point bending tests, a preferential formation of cleavage cracks in samples aged at 175 ℃ and 200 ℃ was identified as the reason for their premature fracture. The X-ray diffraction (XRD) results and transmission electron microscopy (TEM) observations of precipitates indicate that the dominant strengthening precipitates in all peak-aged samples are of the β' phase, and their size significantly influences the formation of cleavage cracks. This phenomenon is attributed to the shearing mechanism of precipitates. Specifically, the smaller β' precipitates formed under the aging temperature of 175–200 ℃ are susceptible to dislocation shearing, leading to the formation of cleavage cracks. In contrast, the larger size of β' precipitates formed under the aging temperature of 225–250 ℃ provides resistance to shearing, resulting in the restrained formation of cleavage cracks and ultimately contributing to the enhancement of the ultimate tensile strength. [ABSTRACT FROM AUTHOR]

• The 18R-LPSO phase is completely refined into sub-micron range by pre-kinking design and large-ratio hot extrusion. • The obtained Mg 97 Y 2 Zn 1 alloy exhibits excellent mechanical properties with ultimate tensile strength of 526 MPa and elongation of 14.5%. • Refinements of Mg grains and 18R-LPSO phase are the main strengthening factors. • The strengthening effect of 18R-LPSO phases increase with their shape changing from blocks to fibers, and to particles. In this study, a composite deformation strategy of pre-kinking (equal channel angular pressing (ECAP)) followed by large-ratio hot extrusion (HE) was designed to refine the 18R long period stacking ordered (LPSO) phase into sub-micron range in a Mg 97 Y 2 Zn 1 (at.%) alloy. After the composite processing, the mechanical properties of the alloy are significantly enhanced, superior to the majority of reported Mg 97 Y 2 Zn 1 and other LPSO-containing Mg alloys. Among the composite deformed alloys, the 16P-HE alloy exhibits the best mechanical properties with tensile yield strength (TYS) of 475 MPa, ultimate tensile strength (UTS) of 526 MPa, and fracture elongation (FE) of 14.5%. Quantitative analysis of 18R phase indicates that increasing ECAP pass from 1 to 16 gradually decreases the average size of 18R phase from 5.1 µm to 2.3 µm. After HE, the 18R phase is further refined with a corresponding decrease in the average size in the descending order of 1P-HE (4.3 µm), 4P-HE (3.2 µm), and 16P-HE (1.4 µm) alloys. Calculation of the strengthening contributions confirms that the superior mechanical properties of 16P-HE alloy are mainly due to its strongest interface strengthening (145 MPa) and grain boundary strengthening (189 MPa) from the sub-micron 18R phase and α-Mg grains. Moreover, the strengthening effect of 18R phase decreases gradually with their morphology changing from particles to fibers, and to blocks. The obtained results further deepen and broaden the strengthening-toughening theory of 18R phase. [Display omitted] [ABSTRACT FROM AUTHOR]

• Single-crystal electrolytic copper foils, with thickness up to 500 µm and facets including both low and high index ones, are first obtained through facet copy from a single-crystal template. • Crystallographic characterizations clearly visualize the facet copy process, where a seed that copy the orientation of the template first grow vertically, and then spread out. • The single-crystal electrolytic Cu foils exhibit remarkably improved mechanical properties than the original ones (elongation-to-fracture: 105% vs. 24%, average numbers of cycles to failure: 1600 vs. 200, and electrical conductivity of 102.6% of the international annealed copper standard (IACS) vs. 98.5%). Depending on the production process, copper (Cu) foils can be classified into two types, i.e., rolled copper (r-Cu) foils and electrolytic copper (e-Cu) foils. Owing to their high electrical conductivity and ductility at low cost, e-Cu foils are employed extensively in modern industries and account for more than 98% of the Cu foil market share. However, industrial e-Cu foils have never been single-crystallized due to their high density of grain boundaries, various grain orientations and vast impurities originating from the electrochemical deposition process. Here, we report a methodology of transforming industrial e-Cu foils into single crystals by facet copy from a single-crystal template. Different facets of both low and high indices are successfully produced, and the thickness of the single crystal can reach 500 µm. Crystallographic characterizations directly recognized the single-crystal copy process, confirming the complete assimilation impact from the template. The obtained single-crystal e-Cu foils exhibit remarkably improved ductility (elongation-to-fracture of 105% vs. 25%), fatigue performance (the average numbers of cycles to failure of 1600 vs. 200) and electrical property (electrical conductivity of 102.6% of the international annealed copper standard (IACS) vs. 98.5%) than original ones. This work opens up a new avenue for the preparation of single-crystal e-Cu foils and may expand their applications in high-speed, flexible, and wearable devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• The high scanning speeds lead to equiaxed and short columnar grains with high dislocation density, while low scanning speeds result in elongated columnar grains with low dislocation density. • The high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion pores, and the excessively low laser scanning speed produces relatively small keyhole pores with high sphericity. • The growth and coalescence of the large lack-of-fusion pores cause the brittle fracture mode and consequent inferior mechanical properties of LPBF-processed Invar 36 alloy. • The decrease in scanning speeds leads to large grain sizes and low dislocation density, slightly reducing the yield strength of LPBF-proessed Invar 36 alloy while enhancing its ductility. Laser powder bed fusion (LPBF) is a potential additive manufacturing process to manufacture Invar 36 alloy components with complicated geometry. Whereas it inevitably introduces specific microstructures and pore defects, which will further influence the mechanical properties. Hence, aiming at exploring the LPBF process-related microstructures and pore defects, and especially their influences on the damage mechanism and mechanical properties, Invar 36 alloy was manufactured by LPBF under designed different laser scanning speeds. The microstructure observations reveal that higher scanning speeds lead to equiaxed and short columnar grains with higher dislocation density, while lower scanning speeds result in elongated columnar grains with lower dislocation density. The pore defects analyzed by X-ray computed tomography (XCT) suggest that the high laser scanning speed gives rise to numerous lamellar and large lack-of-fusion (LOF) pores, and the excessively low laser scanning speed produces relatively small keyhole pores with high sphericity. Moreover, the in-situ XCT tensile tests were originally performed to evaluate the damage evolution and failure mechanism. Specifically, high laser scanning speed causes brittle fracture due to the rapid growth and coalescence of initial lamellar LOF pores along the scanning direction. Low laser scanning speed induces ductile fracture originating from unstable depressions in the surfaces, while metallurgical and keyhole pores have little impact on damage evolution. Eventually, the process-structure-property correlation is established. The presence of high volume fraction of lamellar LOF pores, resulting from high scanning speed, leads to inferior yield strength and ductility. Besides, specimens without LOF pores exhibit larger grain sizes and lower dislocation density at decreased scanning speeds, slightly reducing yield strength while slightly enhancing ductility. This understanding lays the foundation for widespread applications of LPBF-processed Invar 36 alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

• A new loading device was designed to study the corrosion behavior and mechanical property of magnesium-based medical materials under compressive stress (0–6 MPa). • The internal stress gradient stimulates grain boundary migration and lattice rotation, thus promoting grain growth to accommodate plastic deformation. • The degradation mechanism and strengthening mechanism of the Mg-4Li-1Ca alloy under compressive stress were proposed. Biomedical materials may suffer from stress-induced corrosion when performing as implant materials at load-bearing sites, bringing about variations in the microstructure, corrosion resistance, and mechanical properties. In this study, the corrosion behavior and mechanical properties of an extruded Mg-4Li-1Ca alloy were investigated under different micro-compressive stresses (0–6 MPa) using a novel homemade loading device. Under 0–3 MPa of micro-compressive stress, the strong basal texture of extruded Mg-4Li-1Ca alloys was weakened and the internal stress gradient stimulated grain boundary migration to induce grain growth. Meanwhile, increased stress resulted in the precipitation of second-phase particles and the accumulation of residual stress, accelerating the corrosion rate due to preferential corrosion. However, with increasing stress, the volume fraction of the second phase increased, becoming the dominant factor controlling the corrosion rate, and residual stress was released for samples under 4.5–6 MPa of micro-compressive stress. Hence, surface corrosion product films rapidly formed and served as effective physical barriers, weakening the microstructural effect on the corrosion behavior. The yield strength of Mg-4Li-1Ca alloy reached 95.48 MPa under 3 MPa of micro-compressive stress owing to the dual effects of precipitation strengthening and shear-band strengthening. The relationships between microstructure, corrosion behavior, and mechanical property provide a theoretical foundation for understanding the degradation characteristics of the Mg-4Li-1Ca alloy under physiological loading and practical application. [Display omitted] [ABSTRACT FROM AUTHOR]

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• High strength and tough w particle-reinforced Ni-based composites were fabricated via laser-direct energy deposition. • Refining the w particle size to 6.5–12 μm, the tensile strength and elongation of the samples increased to 1347.6 ± 15.7 MPa and 17.5% ± 0.4%. • Proposing a load-transfer efficiency factor suitable for this composite and optimizing the load-transfer strengthening formula. • The article provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites. Tungsten (W) particle-reinforced nickel (Ni)-based composites were fabricated via laser-direct energy deposition (L-DED). The influence of the W particle size on the microstructure and mechanical properties of the deposited samples was systematically studied. The results indicate that refining the W particle size could refine the γ-Ni grains and subgrains, thin the (Ni, Cr)4 W interface layer, and increase the dislocation density of the intergranular matrix, thus improving the tensile strength and elongation of the L-DED samples. As W particle size decreased from 75 to 150 μm to 6.5–12 μm, the tensile strength and elongation of the deposited samples increased by 150 MPa and 2.9 times to 1347.6 ± 15.7 MPa and 17.5 ± 0.4%, respectively. Based on the properties of the interface (Ni, Cr) 4 W, a load-transfer efficiency factor suitable for this composite was proposed and the load-transfer strengthening formula was optimized. A quantitative analysis of the strengthening mechanisms was established considering load-transfer strengthening, Hall–Petch strengthening, thermal-mismatch strengthening, and solid-solution strengthening. The calculated contribution of each strengthening mechanism to the yield strength and theoretical calculations were in good agreement with the experimental data. The article breaks the bottleneck of poor plasticity of W particle-reinforced Ni-based composites prepared by L-DED and provides a theoretical basis for the construction design of W particle-reinforced Ni-based composites with excellent mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

Dispersion-strengthened copper alloys can achieve ultra-high strength, but usually at the expense of ductility. In this study, a strategy for overcoming strength-ductility tradeoff of Cu alloys is realized through the introduction of bimodal grains structures. Cu-Ta alloys with only 0.5 at.% Ta content were successfully prepared by mechanical alloying combined with spark plasm sintering. The samples prepared by one-step and two-step ball milling methods are named as Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ), respectively. The microstructural characterizations revealed that ultra-fine equiaxed grains with uniformly dispersed Ta precipitates were obtained in the Cu-Ta alloys. High strength of 377 MPa for yield strength together with elongation of ∼8% was obtained in Cu-Ta (Ⅰ). Bimodal grains structures composed of fine-grain zones and coarse-grain zones were successfully introduced into Cu-Ta (Ⅱ) by a two-step ball milling approach, and both yield strength (463 MPa) and elongation (∼15%) were significantly synergistic enhanced. The hardness values of both Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ) were almost kept nearly constant with the increase of annealing time, and the softening temperatures of Cu-Ta (Ⅰ) and Cu-Ta (Ⅱ) are 1018 and 1013 °C, reaching 93.9% and 93.5% T m of pure Cu (1083 °C), respectively. It reveals that the Cu-0.5 at.% Ta alloys exhibit excellent thermal stability and exceptional softening resistance. Ta nanoclusters with semi-coherent structures play an essential role in enhancing the strength and microstructural stability of alloys. Bimodal structures are beneficial to the activation of back stress strengthening and the initiation and propagation of microcracks, thus obtaining the extraordinary combination of strength and elongation. This study provides a new way to fabricate dispersion-strengthened Cu alloys with high strength, high elongation, excellent thermal stability and softening resistance, which have potential application value in the field of the future fusion reactor. [Display omitted] [ABSTRACT FROM AUTHOR]

• An ultra-high strength friction stir welded (FSW) joint of twin-induced plasticity steel was obtained, and the mechanical strength was higher than that of basal material. • The deformation behavior of entire FSW joint and the microstructure evolution of micro-zones in FSW joint were investigated by in-situ EBSD at the first time. • The weakest zone of mechanical properties in FSW joint was stir zone, but not heat affect zone, due to the content of annealing twins. The weldability of twin-induced plasticity (TWIP) steel with ultra-high strength via friction stir welding (FSW) technique was investigated, and microstructural evolution and deformation behavior of whole and micro-zones of FSW TWIP joint were studied for the first time. The results showed that the content of recrystallized grains in the stir zone (SZ) increased from 10.5% of basal material (BM) to 14.2%, and that of heat affected zone (HAZ) increased to 78.6%. The percentage of annealing twins decreased from 26.8% in BM to 11% in SZ, while increased to 35% in HAZ. Compared with the BM, the ultimate tensile strength and yield strength of the FSW joint increased to 1036 and 550 MPa, respectively, reaching 106.7% and 110.9% of BM, respectively. The elongation of the entire joint was 50.5%, which was lower than that of BM due to the nonuniform deformation during the tensile test. The engineering strain was mainly concentrated in BM and SZ and transferred to each other during the tensile test, while the engineering strain in HAZ was always the lowest. Finally, the tensile fracture occurred in the SZ. The order of ultimate tensile strength of micro-zones in the FSW joint was as follows: HAZ > BM ≈ SZ. The order of yield strength was as follows: HAZ > BM > SZ. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel series of bio-based, lignin flame retardants (DAL- x) are synthesized. • DAL- x endows epoxy resin with desired flame retardancy and smoke suppression. • DAL- x improves the thermal stability and mechanical properties of epoxy resin. • DAL- x acts in both gas and condensed phases during combustion. Fabricating a high-performing thermoset using bio-based flame retardant is critical for the sustainable development of engineering materials with superior fire safety and robust mechanical properties. Herein, the epoxy (EP) composites with the industrial requirements are manufactured with a novel high-efficient, lignin-based flame retardant named DAL- x , which is fabricated by grafting 9, 10-dihydro-9-oxa-10-phosphaze-10-oxide (DOPO) onto lignin. The resulting DAL- x /EP composite exhibits excellent flame retardancy with a desirable UL-94 V-0 rating and a satisfactory limiting oxygen index (LOI) of 29.8% due to the appropriate phosphorus content of DAL- x with adjustable molecular chain structure. Moreover, the DAL- x /EP composite shows an unexpected improvement in the elastic modulus (∼36%) and well-preserved strength and ductility compared with those of pure EP. This work offers a feasible strategy for creating efficient bio-based flame retardants utilizing industrial waste lignin and preparing high-performance EP composites that meet the demanding requirement of fire retardancy in industries, contributing to the circular economy and sustainability. [Display omitted] [ABSTRACT FROM AUTHOR]

• The mechanical properties and microstructural evolution at 2273 K are reported for the first time among refractory high-entropy alloys/composites. • The deformation mechanisms of the refractory high-entropy composite (RHEC) at 2273 K were analyzed. • The origin of the structural metastability in RHEC the was uncovered. • The effects of structural metastability on the ultrahigh-temperature mechanical properties were revealed. We reported on the mechanical properties and microstructural evolution of a W 20 Ta 30 Mo 20 C 30 (at.%) refractory high-entropy composite (RHEC). The RHEC exhibited outstanding yield strength at both 2273 and 1873 K. Microstructural investigations revealed that the as-cast RHEC had a triple-phase structure consisting of FCC dendrites, HCP matrix, HCP-BCC eutectic structure, and FCC-BCC eutectoid structure, and exhibited high-density defects owing to the complex phase transformations during solidification. After annealing at 2273 K, the precipitation of the BCC phase from the FCC dendrites and the decomposition of the HCP phase into the FCC-BCC eutectoid structure was observed to significantly refine the grain sizes of all triple phases. After compression at 2273 K, the ceramic phases and solid solution precipitated out from each other, which helps to avoid persistent softening after the yielding of RHEC. Further analyses suggested that the dominant deformation mechanisms of the BCC phase and HCP phase are dislocation glide and transformation-induced plasticity; whereas those of the FCC phase are twinning- and transformation-induced plasticity. The outstanding yield strength of this RHEC at ultrahigh temperatures may originate from the high-content ceramic phases and the structural metastability of the multi-principal composition. These findings provide a novel strategy to design RHECs by alloying high-content nonmetallic elements, which contributes to further breaking through their performance limits at ultrahigh temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

• Strong passive film and small potential difference facilitated corrosion resistance. • Ti8.5Cu alloy showed superb anti-bacterial properties (99.2%) against S. algae. • Anti-bacterial activity is mainly due to the ROS rise induced by nano Ti 2 Cu phase. • AM TiCu alloy showed both superb mechanical and MIC resistance in marine environment. The microorganism-rich nature of the ocean imposes great challenges to the structural integrity of metals over their service lifespan, including titanium (Ti) alloys, which are usually prone to microbiologically influenced corrosion (MIC). So, multifunctional anti-MIC Ti alloys need to be developed and studied. This paper investigates the effect of copper (Cu) concentration on the MIC resistance of a series of additively manufactured, ultrafine-grained Ti- x Cu (x = 3.5, 6.5 and 8.5 in wt.%) alloys. The dependence of the corrosion resistance and MIC resistance on the Cu concentration of Ti-Cu alloy is interpreted considering all conceivable mechanisms. The mechanisms for excellent corrosion resistance of Ti-Cu alloy in seawater are attributed to the strong passive film and small surface potential difference between phases. Microstructural characterization reveals that uniformly distributed, nanosized Ti 2 Cu phase led to increased reactive oxygen species in the bacterial membrane, which is the root reason for the superb anti-bacterial property (99.2%) for Ti-8.5Cu. Compared to pure Ti and Ti-6Al-4V, Ti-8.5Cu alloy features both high strength (yield stress > 1000 MPa) and the best MIC resistance (97.5%). The combination of such balanced properties enables this functional 3D printed Ti-Cu alloy to become an ideal material for load-bearing applications in the marine environment. [Display omitted] [ABSTRACT FROM AUTHOR]

• The joint with good mechanical performance in 6061 Al alloy is obtained by shear bonding. • The joint coefficient is over 95%, which was much higher than that of common connection method for Al alloy. • The high joint coefficient is mainly originated from the well-linked joint and gradient grain structure. Obtaining a highly synergistic mechanical property between joint and base metal (BM) in aluminum (Al) alloy is a chronic problem. In this work, shear bonding technology is applied to a commercial 6061 Al alloy. The results show that a flat and uniform joint interface is obtained. The joint presents a highly synergistic mechanical property compared with BM, whether after shear bonding or heat treatment. The joint coefficient reaches 95.6% after shear bonding and exceeds 100% after heat treatment, which is better than the traditional connection method of aluminum alloy. The high joint coefficient mainly originates from the well-linked joint and gradient grain structure. The gradient grain structure is beneficial to activate more slip systems to coordinate plastic deformation. Although the fine-grained structure is sacrificed after heat treatment, higher strength and joint coefficient are obtained due to the higher work hardening. This newly developed method has a large potential for application to the infinite rolling of Al alloy sheets and can also be used for Al alloy connection in automobile, aerospace, rail transportation, and other fields. The findings in this work can provide essential theoretical support and application reference for the shear connection of Al alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

• Dilute Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy sheet was designed to show an admirable balance between anti-corrosion and mechanical properties. • Ce micro-alloying results in lower cathodic activity, better Fe scavenger effect, and denser Ce oxide containing surface film. • Uniform fine-grained structure and ordered Al-Ca-rich G.P. zones are obtained via controlled rolling, solid solution, and aging. • The precipitation of Al-Ca-rich G.P. zones is responsible for pronounced age-hardening response while not causing severe weakening micro-galvanic corrosion. • Inherent strength-corrosion trade-off can be overcome by clever alloying and reasonable thermomechanical processes. Low strength and poor corrosion resistance are two long-standing bottlenecks with dilute Mg alloys. Here, we report that the corrosion resistance of Mg-0.6Al-0.5Mn-0.2Ca (wt.%) alloy sheet can be significantly improved by micro-alloying with 0.3 wt.% Ce, and the strength can be considerably augmented after aging treatment. Simultaneous optimization of strength, ductility, and corrosion resistance is difficult due to the inherent trade-off in Mg alloys. Surprisingly, our aged Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy features with yield strength (YS) of ∼194 MPa, ultimate tensile strength (UTS) of ∼265 MPa, elongation to failure (EF) of ∼17.2%, and corrosion rate (CR) of 2.2 mm y−1, the combination of which exhibits competitive advantage over other comparative dilute Mg alloys. It is found that Ce addition decreases the activity of cathodic phases, inhibits detrimental effects of Fe impurities, and forms a protective Ce-containing surface film. The high strength stems from the precipitation of ordered Guinier-Preston (G.P.) zones dispersed in uniform fine grains with an average grain size of ∼8.2 μm. The atomic-scale G.P. zones result in a noticeable age hardening response but do not act as crack initiation and propagation site, so our alloy also performs satisfactory ductility. This work sheds light on the design and fabrication of strong, ductile, and corrosion-resistant dilute magnesium alloys to be used in electronic products and automotive bodies. [Display omitted] [ABSTRACT FROM AUTHOR]

• The Δ H - δ regions of the HEMGs with low, medium and high glass-forming abilities are proposed. • The reported mechanical and magnetic properties of the HEMGs are summarized and discussed. • The thermal stability, mechanical and functional properties of HEMGs are presented, and the advantages and disadvantages of HEMGs are discussed. High-entropy metallic glass (HEMG) is a new type of metallic material with high-entropy alloy-like composition and amorphous structure, which render HEMGs unusual glass formation behaviors and unique properties. In recent years, fast research progress has been witnessed on the HEMGs, and thus a systematic review is required. In this review, we first introduce the concept of the HEMGs and summarize the developed HEMGs. Then, the glass-forming ability of the HEMGs is discussed, and the general rules are proposed. Focusing on the thermal stability of HEMGs, the effect of entropy on the energy states of HEMGs and the crystallization behavior of HEMGs are discussed. Finally, the mechanical, magnetic, catalytic and other properties of HEMGs are presented, and the advantages and disadvantages of HEMGs are shown. This review can function as a quick guideline for overviewing the HEMG field. [Display omitted] [ABSTRACT FROM AUTHOR]

• A series of novel (Ni 2 Co 2 FeCr) 92- x Ti 4 Al 4 Si x (x = 0, 1, and 2 at%) high-entropy superalloys (HESAs) was developed. • Mitigated intergranular embrittlementwas achieved in the Si-doped HESAs at 700 °C. • Si addition induced a remarkable improvement in the oxidation resistance of HESAs at 700 °C. • Our findings provide a new strategy for designing high-performance HESAs for practical applications. Ti-bearing high-entropy superalloys (HESAs) often suffer from severe intergranular embrittlement and terrible oxidation degradation at intermediate temperatures. Here we showcase that minor Si addition can effectively mitigate the intergranular embrittlement and improve the oxidation resistance of the a (Ni 2 Co 2 FeCr) 92 Ti 4 Al 4 HESA at 700 °C simultaneously. Experimental analysis revealed that the intergranular G phase induced by 2 at% Si addition can effectively suppress the inward diffusion of oxygen along grain boundaries at 700 °C, thus enhancing the tensile ductility of the alloy from ∼8.3% to ∼13.4%. Besides, the 2 at% Si addition facilitated the formation of a continuous Al 2 O 3 layer during oxidation, contributing to a remarkable reduction in the growth rate of the oxide scale to a quarter of the Si-free HESA. Our results demonstrate that Si can be a favorable alloying element to design advanced HESAs with synergistically improved thermal-mechanical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

• Nanosilica is added as filler to improve the overall performance of silicone rubber. • SiO 2 nanoparticles can act as bridges linking more polymer chains. • Nanosilica can decrease free volume and restrict the chain movement of the polymer. • Barrier performance of silicone rubber is also improved by adding nanosilica. • DFT calculations illustrate the exact mechanism of mechanical improvement. Implantable electronic devices (IEDs) are widely used by human beings to achieve medical treatment and diagnosis nowadays. However, ideal encapsulation of IEDs is still far from perfect as full prevention of body fluid diffusion into the coating remains unsolved. Herein, we develop a high-performance composite coating for IED encapsulation by introducing SiO 2 nanoparticles into silicone rubber, which synergistically enhances mechanical properties and improves barrier performance. By fabricating composite coatings with different nanosilica contents, 3% nanosilica is proved to be an optimal additive content with an excellent combination of improved fracture strength (from 2.5 MPa to 4.5 MPa), increased coating resistance (from 104 to 109 Ω cm2) and ideal coating uniformity. Mechanical and electrochemical characterizations subsequently confirm substantially enhanced mechanical properties and barrier performance of the composite coating, which effectively resist crack propagation and impede penetrations of water and chloride ions through the coating. Theoretical calculations further uncover that modified SiO 2 particles with enriched methyl groups endow a strong bridging effect to interact with silicone rubber monomer, which, together with anti-agglomeration property of methyl groups, contributes to a pronounced improvement in mechanical performance of nanosilica-filled silicone rubber. Benefitting from the enhanced mechanical and barrier properties, the as-fabricated nanosilica-filled silicone rubber demonstrates superior protection for the encapsulated circuits with a significantly improved lifetime (709.1 h) compared to that of circuits coated by pure silicone rubber (472.8 h) and bare circuit boards (1 h), which offers great values for packaging material design in future IED encapsulation. [Display omitted] [ABSTRACT FROM AUTHOR]

• Thermodynamic/thermo-physical properties of light-weight RHEAs are covered. • Computational design methods of light-weight RHEAs are introduced. • Preparation/fabrication methods of light-weight RHEAs are reviewed. • Mechanical properties/performance of light-weight RHEAs are summarized. • The design strategy of light-weight RHEAs is proposed. In recent years, high-entropy alloys (HEAs) have become a research hotspot in materials community, and great progress has been made in exploring various high-performance HEAs. As a special class, the light-weight refractory high-entropy alloys (RHEAs) own both excellent high-temperature comprehensive properties and low density and have accordingly attracted more and more attention. In this paper, we presented a comprehensive review of the recent progress and status in light-weight RHEAs. Based on an exhausting search of the literature reports, one strategy in terms of phase numbers after preparation was first proposed to classify the light-weight RHEAs into three categories. Then, the status on the fundamental thermodynamic and thermophysical data/databases, computational approaches for alloy designing, and preparation/fabrication techniques of light-weight RHEAs was introduced one after another. After that, the progress on mechanical properties and oxidation/corrosion/wear behaviors of light-weight RHEAs at room and high temperatures was summarized. Finally, the conclusions of this review were drawn. By pointing out the shortcomings of the current research, the follow-up development directions in the field of light-weight RHEAs were also given. [ABSTRACT FROM AUTHOR]

• An E of 90–265 J/mm3 is suggested to achieve high relative density. • Primary γ austenite increases and residual δ ferrite reduces as the E increase. • An increase in E helps to obtain superior mechanical and shape memory properties. • Ultrahigh mechanical properties result from multiple strengthening mechanisms. • A high recovery strain of about 6% was achieved. This work systematically studied the effect of volumetric energy density E on the densification, microstructures, tensile mechanical properties, and shape memory performance of a Fe-Mn-Si-Cr-Ni shape memory alloy (SMA) fabricated by laser powder bed fusion (L-PBF). An E of 90–265 J/mm3 is suggested to fabricate the Fe-Mn-Si-Cr-Ni SMA with minor metallurgical defects and a high relative density of above 99%. The increase in E can promote the formation of the primary γ austenite and the solid phase transformation from the primary δ ferrite to the γ austenite, which helps to achieve a nearly complete γ austenitic microstructure. The increase in E also contributes to fabricating the Fe-Mn-Si-Cr-Ni SMA with superior comprehensive mechanical properties and shape memory performance by L-PBF. The Fe-Mn-Si-Cr-Ni SMA with a combination of good ductility of around 30%, high yield strength of above 480 MPa, an ultrahigh ultimate tensile strength of above 1 GPa, and large recovery strain of about 6% was manufactured by L-PBF under a high E of 222–250 J/mm3. The good shape memory effect, excellent comprehensive mechanical properties, and low cost of Fe-Mn-Si-Cr-Ni SMAs, as well as the outstanding ability to fabricate complex structures of L-PBF technology, provide a solid foundation for the design and fabrication of novel intelligent structures. [Display omitted] [ABSTRACT FROM AUTHOR]

• Microstructure entirely consists of fine equiaxed grains, reducing the anisotropy of tensile properties. • σ UTS , σ y , and elongation reach 618 MPa, 542 MPa, and 5.7% after T6 heat treatment. • The highest tensile and yield strengths achieved among the existing reported WAAM aluminum alloys. The utilization of wire-arc additive manufacturing (WAAM) technology for the preparation of Al-Zn-Mg-Cu aluminum alloy has made some progress in recent years. However, the challenge still remains to achieve ultra-high strength (600 MPa) in WAAM. In this study, the crack-free Al-Zn-Mg-Cu- Sc thin-wall component with ultra-high strength was successfully fabricated by the cold metal transfer (CMT) process using a self-prepared 7B55- Sc filler wire. The microstructures of both as-deposited and T6 heat-treated samples were all composed of fine equiaxed grains with an average size of about 6.0 μm. The primary Al 3 (Sc , Zr) particles acted as heterogeneous nuclei to promote the formation of equiaxed grains and refine the microstructures during the solidification process. A large amount of continuous eutectic structures rich in Al, Zn, Mg, and Cu elements formed along the grain boundaries under the as-deposited condition, and the precipitated second phases within the grains mainly included the equilibrium η phase, metastable η ′ phase and large-sized T phase. After T6 heat treatment, the majority of the second phases originally distributed within grains and along grain boundaries were dissolved into the Al matrix, and a large amount of fine GP zones, η ′ phase and secondary Al 3 (Sc ,Zr) particles were precipitated within the grains during the aging process. The tensile strength reached a recorded level of 618 MPa in the horizontal direction after T6 heat treatment, which was considered a breakthrough for the manufacturing of 600 MPa grade aluminum alloy by WAAM. [Display omitted] [ABSTRACT FROM AUTHOR]

• High-strength aluminum alloys via laser powder bed fusion are on demand for industrial applications. • Addition of Sc in aluminum alloys can achieve hitherto the highest range of strength with good laser powder bed fusion processability. • Sc addition plays a critical role in forming unique microstructure in strengthening Al alloys. Laser powder bed fusion (LPBF) is one of the typical additive manufacturing techniques that enables the fabrication of complex-shaped structures with great freedom of design. Due to the challenges encountered in LPBF processing of Al alloys, most studies have focused on AlSi alloys which are much easier to process but are not inherently designed for high-strength applications. In recent years, however, significant progress has been made to develop Sc -containing Al alloys that are designed specifically for LPBF production. These alloys display excellent processability and superior mechanical properties that open up a range of possible applications in industries that require high specific strength, good thermal stability, and increased functionality. As such, this paper reviews the available literature on how Sc additions influence the microstructure and properties of Al alloys when processed via LPBF and thus, aims to shed light on the considerations that have been made to achieve remarkable material consolidation alongside excellent mechanical properties, with the latter achieved through a high degree of Sc supersaturation and a great potential for nanoprecipitation. [Display omitted] [ABSTRACT FROM AUTHOR]

Nb-Si based alloys have the greatest potential to replace nickel-based superalloys and become a new generation ultra-high temperature structural material with service temperature of 1200-1400 °C due to their high melting point, high stiffness, low density, and attractive specific mechanical properties at elevated temperatures. This article reviewed the recent progress in the development of Nb-Si based refractory alloys. Special attention was paid to the property characteristics, preparation techniques, alloying effects, oxidation resistance and fabrication of Nb-Si based alloy components. Thereafter, the trend of development in the future was forecasted, including: Optimization of the composition and microstructure of Nb-Si based alloys to achieve a balance of mechanical properties; Comprehensive properties evaluation for Nb-Si based alloys to accumulate sufficient data for engineering applications; Development of practical preparation technology for Nb-Si based alloy components with complex shapes; New multilayer composite coatings for Nb-Si based alloy; Joining technology of Nb-Si alloy to itself and to superalloy. [ABSTRACT FROM AUTHOR]

• The first time that using laminated structure strategy to achieve strength-ductility synergy in BMGCs. • The strength-ductility synergy is due to asynchronous deformation arising from inter-laminar and intra-laminar. • Dual-scale ta particles that uniformly distribute on the amorphous matrix also contribute to improving mechanical properties. Introducing ductile crystalline dendrites into a glassy matrix to produce bulk metallic glass composites (BMGCs) is an effective way to improve the poor ductility of bulk metallic glasses (BMGs). However, the presence of soft crystalline phases tends to decrease the strength and causes the strength-ductility tradeoff. Here, relying on the flexible laser additive manufacturing (LAM) technique that allows the composition tailoring of each layer, we successfully fabricate a lamellated Zr-based BMGC constructed by the alternating superimposition of soft and hard layers. The lamellated BMGC shows an exceptional combination of yield strength (∼1.2 GPa) and ductility (∼5%). Such enhanced strength-ductility synergy is attributed to the asynchronous deformation at two scales, i.e., inter-laminar and intra-laminar, and the unique dual-scale Ta particles that uniformly distribute on the amorphous matrix. The lamellated structure design motif, enabled by the flexible LAM technology, provides a new window for the development of high-performance BMGCs. It is also applicable to the synergistic enhancement of strength and plasticity of other brittle metallic materials. [ABSTRACT FROM AUTHOR]

• The multi-scale structured Zn-0.4Mn-0.8Li alloy was fabricated by hot rolling. • The cooperation of coarse grains and fine grains was found to improve the strength and guarantee the ductility of Zn-0.4Mn-0.8Li alloy significantly. • The activation of {10-12} tensile twinning further promoted the enhancement of the mechanical strength of Zn-0.4Mn-0.8Li alloy. Zinc-based degradable metals are considered one of the most promising biodegradable materials due to their moderate corrosion rate, excellent mechanical properties, and good biocompatibility. In this work, biodegradable Zn-0.4Mn-0.8Li alloy was fabricated and rolled in multiple passes at different temperatures. As the hot rolling temperature increases, the grain size of Zn-0.4Mn-0.8Li alloy was found to increase correspondingly. Further, a multi-scale structure with the coexistence of coarse grains and fine grains was obtained. The results demonstrated that the mechanical strength and corrosion resistance were improved by increasing the rolled temperature. It was observed that Zn-0.4Mn-0.8Li alloy with a total reduction of 90% after hot rolling at 325 °C exhibited excellent mechanical and corrosion properties. The cooperation of multi-scale microstructure and twinning was found to improve the strength and guarantee the ductility of Zn-0.4Mn-0.8Li alloy significantly so that the 325 °C hot-rolled Zn-0.4Mn-0.8Li alloy has optimal comprehensive properties. Further, yield strength, ultimate tensile strength, and elongation were found to be 449.7 ± 5.3 MPa, 505.1 ± 6.5 MPa, and 40.5% ± 7.5%, respectively. Meanwhile, Zn-0.4Mn-0.8Li alloy via 325 °C hot-rolled processes also exhibited excellent corrosion resistance. The corrosion current density and corrosion potential were found to be 8.8 × 10–5 mA cm–2 and −0.929 V, respectively. The preliminary study indicates that Zn-0.4Mn-0.8Li alloy is a promising candidate material for medical device applications. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel in-situ reactive approach based on the reactions among TiN, aluminum and boron has been developed to synthesize TiB 2 -based composites including TiB 2 - h BN (TB) and TiB 2 - h BN-AlN (TBA). Fully dense ceramics with fine-grained microstructure were successfully obtained via spark plasma sintering at 1850 °C/60 MPa/5 min. Microstructure analysis suggests h BN flakes were homogenously distributed in the TiB 2 matrix. For AlN, however, they were elongated into plate-like grains during sintering, in which lots of defects in terms of stacking faults and twinning structures were observed. The mechanical and thermophysical properties of as-sintered ceramics were comprehensively investigated and compared. Incorporating AlN significantly improved the flexure strength, hardness, fracture toughness and thermal conductivity of TiB 2 - h BN ceramics. The electrical conductivity of TB (3.06 × 106 S/m) is larger than that of TBA (2.35 × 106 S/m) at room temperature, but the value (6 × 105 S/m) was lower than that of TBA (6.9 × 105 S/m) at 1173 K. Based on the measurement of electrical and thermal conductivity, electron and phonon contributions to thermal conductivities of TB and TBA were calculated and their temperature dependences were illustrated. [ABSTRACT FROM AUTHOR]

• Yield strength of materials can be greatly improved after pre-strain and baking. • Dislocation as fast channels for carbon diffusion promotes cementite formation. • Carbon clusters gathered at the dislocations act as precursors of cementite. • Cementite precipitation is main reason for increase in strength of bainite steel. In the automobile industry, stamping and paint baking processes are used to strengthen components, and this not only saves costs, but also further reduces the bodyweight of automobiles. In this work, the bake hardening mechanism of the complex phase (CP) steel CP980 was explored by comparing it with that of DP1180, which has a clear bake hardening mechanism and a carbon content similar to that of CP980. By analyzing the bake hardening response and the microstructural changes of the two steels, we found that the bake hardening process of CP980 was divided into three stages. In the first two stages, the carbon atoms diffused into dislocations to form Cottrell atmosphere pinning dislocations, and excess carbon atoms formed carbon clusters or low-temperature carbide pinning dislocations that were similar to DP1180. In the third stage, the dislocation acted as rapid channels for carbon diffusion, and fine cementite gradually formed when the carbon clusters gathered at the dislocations as precursors, resulting in precipitation hardening. This novel bake-hardening (BH) mechanism is crucial for obtaining a comprehensive understanding of the strain-baking behavior of advanced high-strength steals (AHSS). [Display omitted] [ABSTRACT FROM AUTHOR]

• Combined process of SPDT and SPS diffusion bonding can realize high-strength Cu-Cu bonding of 271 MPa at 202 °C. • A new mechanism is proposed that the pulsed current significantly promotes the closure of interfacial micro-voids during the SPS diffusion process. • A new "evaporation-deposition" mechanism for the closure of interfacial nano-voids during SPS diffusion bonding is proposed. • Molecular dynamics simulations show that energetic atoms promote the void closure during SPS diffusion bonding. In this study, combining the single point diamond turning (SPDT) and spark plasma sintering (SPS), we achieved high-strength diffusion bonding of copper at an ultra-low temperature of 202 °C (0.35 T m , T m : absolute temperature of the melting point). Additionally, the closure mechanism of interfacial micro- and nano-voids during the Cu–Cu SPS diffusion bonding is systematically revealed for the first time. For micro-voids, the pulsed current is found to induce additional diffusion flux and plastic deformation, thereby facilitating the void closure. Molecular dynamics (MD) simulation revealed that at the atomic scale, high-energy Cu atoms induced by the pulsed current can significantly promote the diffusion of low-energy atoms in their vicinity and accelerate the void closure. This study also proposes a novel "evaporation–deposition" nano-void closure mechanism for the previously unstudied nano-void closure process. The results show that the synergistic effect of the pulsed current and nanoscale surface roughness can significantly improve joint strength. At a low temperature of 405 °C (0.5 T m), on combining the computerized numerical control (CNC) turning and SPS diffusion bonding, the joint strength can reach 212 MPa, while that for the joint obtained by traditional hot pressing diffusion bonding at the same temperature is only 47 MPa. We obtained an ultra-high joint strength of 271 MPa using the combined process of SPDT and SPS diffusion bonding at an ultra-low temperature of 202 °C (0.35 T m), which is approximately 600 °C lower than the traditional diffusion bonding process temperature of 800 °C (0.79 T m). To sum up, this study provides a novel method and theoretical support for realizing low-temperature high-strength diffusion bonding. [ABSTRACT FROM AUTHOR]

The microstructural modification for cellular structures can achieve the improvement of dynamic mechanical properties of a selective laser melted FeCoNiCrMo 0.2 high-entropy alloy (SLM-FeCoNiCrMo 0.2 HEA) and can expand its promising applications in the field of high-velocity deformation. In this work, FeCoNiCrMo 0.2 HEAs with cellular structures in different sizes were produced by selective laser melting (SLM) with different process parameters. The dynamic mechanical properties and microstructure of the SLM-FeCoNiCrMo 0.2 HEA were studied. The dynamic mechanical properties of the SLM-FeCoNiCrMo 0.2 HEA increased with decrease of average size of cellular structures, and the values of them were sensitive to strain rates. The energy absorption, compressive strength and yield strength of the SLM-FeCoNiCrMo 0.2 HEAs reached 315.6 MJ/m3, 2.2 GPa and 775.6 MPa, respectively at a strain rate of 2,420 s−1, under the process parameters of laser power and scanning speed of 330 W and 800 mm/s, respectively, where the corresponding average size of cellular structures in the HEAs was 483.6 nm. The value of strain-hardening rate of the SLM-FeCoNiCrMo 0.2 HEA was about 5.1 GPa at a strain level of 0.1, which was much higher than that of the powder-metallurgy FeCoNiCrMo 0.2 HEA. The cellular structure was formed inside the molten pool with segregation of Mo on the boundary. Deformation localization appeared in the cellular structures, forming several deformation bands after high strain-rate deformation. The elemental segregation strengthening and dislocation strengthening are considered to be the main strengthening mechanisms in SLM-FeCoNiCrMo 0.2 HEA. [ABSTRACT FROM AUTHOR]

• Micro-cracks are along the GBs in PBF-LB Al-HEAs due to the residual liquid film therein with an increased solidification temperature range by Al addition. • Al/Ni/Mn decorated dislocation cells exist in the as-built Al-HEAs and massive BCC phases precipitate at the dislocation cell/grain boundaries upon heat treatment. • Al-HEA850 exhibits the highest strength and the lowest corrosion resistance due to the massive precipitates. With the development of aerospace and transportation, high-strength structural materials manufactured by additive manufacturing techniques get more attention, which allows the production of counterparts with complex structures. This work investigates Al-added CoCrFeMnNi high-entropy alloys (Al-HEAs) prepared by laser powder bed fusion (PBF-LB), adding 4.4 wt.% Al reducing approximately 7% density. The contribution of post-heat-treatment to microstructure, mechanical properties, and corrosion behaviors are explored. Hot cracking along with grain boundaries in the as-built PBF-LB Al-HEAs is determined, which comes from the residual liquid film as a larger solidification temperature range by adding Al. The PBF-LB Al-HEAs mainly consist of a face-centered cubic (FCC) matrix with Al/Ni/Mn decorated dislocation cells therein and a minor body-centered cubic (BCC) phase. Upon 850 °C annealing treatment, massive BCC phases (ordered NiAl and disordered Cr-rich precipitates) generate at the dislocation cell/grain boundaries and the dislocation cells are still retained. However, the volume fraction of BCC phases and the dislocation cells vanish after 1150 °C solution treatment. As a result, Al-HEA850 shows an over 1000 MPa yield strength with nearly no ductility (<3%); the Al-HEA1150 exhibits considerable strength-ductility properties. Meanwhile, the Al-HEA850 demonstrates the worst pitting corrosion resistance due to the preferential dissolution of the NiAl precipitates in chloride-containing solutions. After comparatively deliberating the evolution of strength-ductility and localized corrosion, we built a framework about the effects of the heat treatment on the mechanical property and degradation behavior in additively manufactured Al-added high-strength HEAs. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel cross-scale hierarchical microstructure is achieved in additively manufactured HEA composites reinforced with nano-scale TiC. • The incorporation of different contents of nano-scale TiC particles into the HEA matrix allows for literally tailoring the morphology of this hierarchically structured microstructure. • The strength and ductility of additively manufactured HEA composites are synergistically improved. • The introduction of nano-scale TiC into the HEA matrix overcomes the strength-ductility trade-off via eliminating the formation of oxide inclusions and exploiting multiple strengthening mechanisms. • Dislocation strengthening contributes most (∼40%) to the improvement of strength of HEA composites due to the severe sluggish diffusion effect and lattice distortion inherent to HEA materials. High entropy alloys (HEAs) have recently received extensive attention due to their appealing mechanical performance given their simple phase formation. This study utilized laser powder bed fusion (LPBF) to fabricate high-performance HEA components. By processing respective powder blends, LPBF enabled the fabrication of stronger composites with a uniformly distributed reinforcing phase. Here, the impact of varying content of nano-scale TiC (1–3 wt%) particles for strengthening the CoCrFeMnNi HEA was explored. The microstructural features and mechanical properties of the HEA composites were investigated in detail. The introduction of nano-scale TiC into the HEA matrix encouraged the development of cross-scale hierarchical microstructure and eliminated the formation of oxide inclusions. Incorporating more nano-TiC led to a higher dislocation density and more refined microstructure in the HEA composites, whereas it posed little influence on the anisotropy of the HEA matrix which typically featured a 〈001〉 texture along the building direction. With an optimized content of nano-TiC (1–2 wt%), the strength-ductility trade-off can be overcome by exploiting multiple strengthening mechanisms encompassing grain boundary strengthening, solid solution strengthening, Orowan strengthening, and dislocation strengthening. The HEA composites showed a favored strength-ductility combination with a yield strength of 748–882 MPa, ultimate tensile strength of 931–1081 MPa, and fracture elongation of 23%–29%. This study demonstrates that the introduction of nano-scale TiC is an effective way to simultaneously improve the strength and ductility of additively manufactured HEA materials. [ABSTRACT FROM AUTHOR]

• A power spinning process and subsequent three kinds of heat-treatment routines were conducted on the new duplex Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy. • The microstructure evolution and mechanical properties of low-cost titanium alloy were systematically studied. • The as-spun specimens, subjected to low-temperature annealing at 550 °C for a duration of less than 4 h, exhibited a good balance of strength and ductility. • The irregular variation of elongation can be ascribed to the competition of precipitation and spheroidization. The microstructural evolution and mechanical properties of low-cost Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy during power spinning and after three types of heat-treatment routines (low-temperature annealing, high-temperature annealing, solution and annealing) were systematically studied. An effective heat-treatment routine to fabricate high-strength and acceptable ductile as-spun Ti-5.5Al-1Fe-3.5Cr-3.2Zr-0.2Si alloy tubes was then proposed whereby the relationship between the mechanical performances and microstructures was analyzed. The {0002} α and {001} β textures were formed after multi-pass power spinning. The as-spun LC-Ti alloy exhibited a good combination of strength and elongation after heat treatment at 550 °C for 4 h, which was ascribed to the large plastic induced low-temperature spheroidization of deformed α phase and nanoscale α precipitation from deformed β phase. However, the elongation decreased evidently when Zr2Si/TiCr2 participated at the interphase boundaries after heat treatment at 550 °C for 8 h. In high-temperature annealing, the elongation changed nonlinearly owing to the precipitation of Zr2Si particles at triangular grain boundaries treated at 750 °C for 1 h, and the spheroidization of the deformed α p phase. Under solution and annealing conditions, lenticular α s would participate from the metastable β grains, which contributed to the greatest strength albeit poor ductility. This study provides an effective guidance for the processing and application of the low-cost titanium alloy. [Display omitted] [ABSTRACT FROM AUTHOR]

• The whole microstructural evolution during extrusion of Mg-Ce alloy was uncovered in this work. • Profuse < c + a > dislocations have been activated in Mg-Ce alloy, which is different from < a > dislocations formed in pure Mg. • The LAGB formation process related to < c + a > dislocations movement was directly observed by EBSD and TEM images. • A novel Mg-Ce wrought alloy with high strength-ductility synergy has been obtained. Constructing bimodal grain structure is a promising approach to achieve the high strength-ductility synergy in Mg alloy. Formation of bimodal grain is closely related to the dynamic and/or static recrystallization process, which has not been fully understood in the typical Mg-RE based alloy. In this work, it is claimed for the first time that the minor Ce addition (∼0.3 wt%) into Mg matrix significantly promotes the pyramidal and non-basal dislocations at the early stage of extrusion, which consequently enhances the formation of sub-grain boundaries via the movement and recovery of pyramidal II-type dislocations. At this stage, fine sub-grain lamellae are widely observed predominantly due to the low migration rate of sub-grain boundary caused by the limited mobility of dislocations. At the later stage, the sub-grains continuously transform into dynamic recrystallized (DRXed) grains that have 〈 10 1 ¯ 0 〉 Taylor axis and also strong fiber texture, indicating substantial activation of pyramidal II-type dislocation. The low mobility of dislocations, accompanied with the solute drag from grain boundary (GB) segregation and pinning from nano-phases, cause a sluggish DRX process and thus a bimodal microstructure with ultra-fined DRXed grains, ∼0.51 µm. The resultant texture hardening and grain refinement hardening effects, originated from bimodal microstructure, result in a yield strength of ∼352 MPa, which is exceptional in Mg-Ce dilute alloy. This work clarifies the critical role of Ce addition in tuning recrystallization behavior and mechanical property of magnesium, and can also shed light on designing the other high-performance Mg alloys. [ABSTRACT FROM AUTHOR]

• High entropy alloy was strengthened by cryo-pre-straining-induced defects. • Strengthening mechanism was quantitatively revealed by neutron diffraction method. • Selective recovery of crystal defects assist to optimize the mechanical performance. Owing to their attractive structure and mechanical properties, high-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted considerable research interest. The strength of HEAs/MEAs with a single face-centered cubic (FCC) phase, on the other hand, requires improvement. Therefore, in this study, we demonstrate a strategy for increasing the room-temperature strength of FCC-phase HEAs/MEAs by tuning cryo-pre-straining-induced crystal defects via the temperature-dependent stacking fault energy-regulated plasticity mechanism. Through neutron diffraction line profile analysis and electron microscope observation, the effect of the tuned defects on the tensile strength was clarified. Due to the cryo-rolling-induced high dislocation density, mechanical twins, and stacking faults, the room-temperature yield strength of an equiatomic CoCrFeNi HEA was increased by ∼290%, from 243 MPa (as-recrystallized) to 941.6 MPa (30% cryo-rolled), while maintaining a tensile elongation of 18%. After partial recovery via heat treatment, the yield strength and ultimate tensile strength decreased slightly to 869 and 936 MPa, respectively. Conversely, the elongation increased to 25.6%. The dislocation density and distribution of the dislocations were found to contribute to the strengthening caused by forest dislocations, which warrants further investigation. This study discussed the possibility of developing single-phase high-performance HEAs by tuning pre-straining-induced crystal defects. [ABSTRACT FROM AUTHOR]

• The dual-phase high-entropy ceramics (HECs) were first designed and fabricated using reaction-driven inter-diffusion processes among ZrB 2 , HfB 2 , NbB 2 , TaB 2 , and TiC. • The inhomogeneity of element distribution in boride and carbide phases was quantitatively investigated. • The novel diboride-carbide HECs showed outstanding mechanical properties as compared with other single-phase HEC samples. Fully dense dual-phase high-entropy ceramics (HECs) were fabricated by hot-pressing at 2000 °C for 1 h based on the in-situ reaction and solid solution processes among equimolar ZrB 2 , NbB 2 , HfB 2 , TaB 2 and 30–70 mol% TiC. The negligible porosity, fine grain size, and plate-like diboride grains are found by microstructure observation. The element distribution is not uniform in different phases: Ti and Nb are enriched in the diboride phase, while Zr, Hf, and Ta are preferentially dissolved into the carbide phase. The reactive sintering dual-phase HECs exhibit superior mechanical properties of hardness 28.4 ± 1.5 GPa, flexural strength 1017 ± 91 MPa, elastic modulus 565 GPa, and fracture toughness 4.7 ± 0.3 MPa m1/2, respectively, which surpass most of diboride and carbide high-entropy ceramics in the previous reports. [ABSTRACT FROM AUTHOR]

Previous experiments have revealed that the controllable introduction of structural gradients in metallic glasses (MGs) can endow the materials with extra plasticity due to the gradient-induced deflection of shear bands. However, the relation between the spatial structural gradient and the initiation of shear band deflection remains unclear. The current study has been focused on investigating the relationship between the improved mechanical properties of MGs and structural gradients specified by the distribution of the intrinsic free volume. Molecular dynamics (MD) simulations are firstly performed on homogeneous MG models containing various initial free volume values, showing that the shear band angle increases with decreasing free volume under uniaxial compression, whereas higher shear band angle is observed under uniaxial tension with increasing free volume. Based on the asymmetric behaviors of MGs under compression and tension, a theoretical model is developed to quantitatively characterize the influence of free volume on the mechanical response of MGs, which incorporates a failure criterion based on free volume generation during external loadings. The model can be further utilized to interpret and predict the fracture strain, shear band angle, maximum stress, and fracture surface morphology of gradient structured MGs in both simulations and experiments. The relationship between free volume gradient and shear band deflection induced extra plasticity established in this study provides valuable guidance for the structural design of MGs with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

• The response of mechanical property to the microstructure variation was analyzed. • The grain refinement induced by CDRX and secondary phases was illustrated. • The strengthening mechanism caused by microstructure evolution was revealed. • A strategy to produce Al–Mg alloys with high mechanical performance was provided. In this work, the mechanical properties and strengthening mechanisms induced by microstructural evolution in a rheo-extruded 5087 alloy processed via accumulative continuous extrusion forming (ACEF) were investigated. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) were utilized to characterize the microstructure of the alloy subjected to ACEF with various passes. The grain refinement caused by continuous dynamic recrystallization (CDRX) was discussed. The results demonstrated that after 3 passes of ACEF, there was a significant grain refinement effect on the alloy, and the average grain size decreased from 45.6 μm to 2.5 μm; the ultimate tensile strength (UTS) and yield strength (YS) of the alloy increased to 362.8 MPa and 234.6 MPa, respectively. Dislocation cells/walls generated during deformation promoted the formation of low angle grain boundaries (LAGBs). The accumulative strain accelerated the transformation of LAGBs to high angle grain boundaries (HAGBs). Dislocation pile-up enhanced the driving force of CDRX, and nano-sized Al 6 (Mn, Fe) phases at the grain boundaries inhibited the growth of grains due to the pinning effect. Based on the quantitative estimation, dislocation strengthening and grain boundary strengthening dominated the enhancement in YS of the ACEFed alloy. [ABSTRACT FROM AUTHOR]

• NiCoCrFeMoW HEAs with high density and sound velocity were developed. • Excellent quasi-static tensile and dynamic compression properties were achieved. • The dynamic flow behavior was successfully described by modified Johnson-Cook model. • Microbanding and twinning make major contribution on dynamic strengthening. High density alloys with enhanced deformability and strength are urgently required in energy, military and nuclear industries, etc. In this work, we present a new kind of NiCoFeCrMoW high entropy alloys (HEAs) which possess higher densities and sound velocities than copper. We systematically investigate the phase structure, quasi-static tensile, dynamic compression and related deformation mechanism of these HEAs. It is shown that single FCC or FCC + μ dual phases were formed in the HEAs depending on Mo and W content and annealing temperature. Excellent quasi-static tensile and dynamic compression properties have been achieved for these HEAs, e. g. Ni 30 Co 30 Fe 21 Cr 10 W 9 HEA annealed at 1573 K exhibited a yield and ultimate tensile strength and elongation of ∼364 MPa, ∼866 MPa and ∼32%, respectively, in quasi-static test; a yield strength of ∼710 MPa and no fracture under the dynamic strain rate of 4100 s−1. Superior strain rate sensitivity (SRS) of yield strength than that of previously reported FCC HEAs have been evidenced. The dynamic stress-strain constitutive relation can be described by the modified Johnson-Cook model. As for the dynamic deformation mechanism, it is envisaged that the regulation of stacking fault energy and Peierls barrier in current HEAs resulted in occurrences of abundant nanoscale deformation twins and microbands during high strain rate compression. The synergistic microbanding and twinning effectively contributes to the enhanced dynamic deformability and strengthening effect. Besides, the interactions of dislocations with precipitates, stacking faults (SFs) with twins, and between SFs also contribute to extraordinary work-hardening capacity. [Display omitted] [ABSTRACT FROM AUTHOR]