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• Tungsten alloy with a CoCrFeNi high entropy alloy binder was deposited via the laser metal deposition method. • Typical solidification microstructures were elucidated via the CALPHAD method. • The nano precipitate and intermetallic compound layer were characterized. • The alloy exhibits a rarely high compressive stress of 2047 MPa and strain of 32 % at room temperature. Tungsten heavy alloys (WHAs) prepared using laser additive manufacturing (AM) exhibit intricate geometries, albeit with limited mechanical properties. Here we designed a high-strength WHA featuring a FeCrCoNi high entropy alloy (HEA) binder via the laser metal deposition (LMD) technique. Due to the distinctive thermal cycle and rapid cooling rate, the as-deposited alloys exhibit microstructures with hypoeutectic, eutectic-like, and spot-like characteristics. To elucidate this phenomenon, the solidification paths were delineated and analyzed by combining microstructural characterization and phase equilibrium simulation. The μ phase precipitated out from the supersaturated solid solution, thereby nucleating massive dislocations on the FeCrCoNi matrix to increase the work hardening rate. Furthermore, the μ phase formed an ultrafine intermetallic compound (IMC) layer around the W grain, reducing the hole or crack between the W grain and FeCrCoNi matrix. Attributed to the precipitation strengthening, the solid solution of the FeCrCoNi binder, along with the load-bearing strength of W, the developed alloy achieved ultrahigh compressive stress and strain of 2047 MPa and 32 % respectively at room temperature. These findings contribute valuable insights to the advancement of additive manufacturing for tungsten alloys, leveraging their excellent properties. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel stacking faults-dominated deformation mechanism was discovered. The increased flow strength is correlated with stacking fault density or spacing. Accurate equations for stacking fault strengthening were established. As a kind of planar defect, stacking faults are seldom explored. Quantitatively evaluating the correlation between stacking faults (SFs) and strength remains unclear. In the present work, we conducted tensile tests at specified true strains and characterized deformation microstructures for a nonequiatomic CoCrNi alloy with very low stacking fault energy (SFE). Characteristics of stacking fault spacing, stacking fault density, and stacking fault strengthening quantification were investigated. This work provides a reasonable reference for the quantitative calculation of stacking fault strengthening. [ABSTRACT FROM AUTHOR]

• Machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs. • Two-stage aging parameters of 400 °C/75 min + 400 °C/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy, resulting in a tensile strength of 875 MPa and a conductivity of 41.43 %IACS, respectively. • The evolution of CPs and DPs and their effects on alloy properties were clarified to get a reasonable quantitative control target of precipitates. Recent studies have shown that synergistic precipitation of continuous precipitates (CPs) and discontinuous precipitates (DPs) is a promising method to simultaneously improve the strength and electrical conductivity of Cu-Ni-Si alloy. However, the complex relationship between precipitates and two-stage aging process presents a significant challenge for the optimization of process parameters. In this study, machine learning models were established based on orthogonal experiment to mine the relationship between two-stage aging parameters and properties of Cu-5.3Ni-1.3Si-0.12Nb alloy with preferred formation of DPs. Two-stage aging parameters of 400 °C/75 min + 400 °C/30 min were then obtained by multi-objective optimization combined with an experimental iteration strategy, resulting in a tensile strength of 875 MPa and a conductivity of 41.43 %IACS, respectively. Such an excellent comprehensive performance of the alloy is attributed to the combined precipitation of DPs and CPs (with a total volume fraction of 5.4 % and a volume ratio of CPs to DPs of 6.7). This study could provide a new approach and insight for improving the comprehensive properties of the Cu-Ni-Si alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

• oriented grains with high aspect ratio" is proposed to break strength-conductivity trade-off. • Directional solidification and serious drawing construct grain with high aspect ratio and strong <111> texture. • Cu wire achieves remarkable combination of yield strength (482.3 MPa) and conductivity (101.63 % IACS). Simultaneously improving the strength and electrical conductivity of conducting metallic materials is of great significance, but it still remains a key challenge as the two properties are often mutually exclusive. In this study, we demonstrate a "<111> oriented fibrous grains with ultra-high aspect ratio" strategy for breaking such a conflict in Cu wire, which relies on the distinctive spatial distribution of grain boundaries and the highly consistent hard orientation to play their respective roles in suffering loading and conducting, thereby enabling a separate optimization of both strength and electrical conductivity. Therefore, a processing route was designed, involving directional solidification followed by large drawing deformation, to successfully construct fibrous grains with an ultra-high aspect ratio in 596.7 and ultra-high <111> texture proportion over 97 %, which achieves Cu wire with a remarkable combination of yield strength in 482.3 MPa and electrical conductivity in 101.63 % IACS. Finally, the mechanisms for high strength and high electrical conductivity were quantitatively discussed. [Display omitted] A strategy of "<111> oriented fibrous grains with ultra-high aspect ratio" is demonstrated to break the conflict between strength and conductivity. Accordingly, a processing route is designed, involving directional solidification and large deformation drawing, to construct fibrous grains with ultra-high aspect ratio and ultra-strong <111> texture, enabling Cu wire with a remarkable combination of yield strength (482.3 MPa) and conductivity (101.63%IACS). [ABSTRACT FROM AUTHOR]

• An unreported nanoribbon reinforced carbon/carbon composite is produced. • Comparison of enhancing efficiency of nanoribbons and nanowires is conducted. • Nanoribbons can simultaneously enhance strength and toughness of carbon/carbon composites. • Nanoribbons show significant advantageous in deflecting cracks compared to nanowires. Incorporating one-dimensional (1D) nanofillers into carbon/carbon composites (C/Cs) can increase their mechanical strength. However, this method is ineffective in improving the fracture toughness of C/Cs because cracks can easily pass over the 1D nanofillers, resulting in a flat fracture surface. Herein, we propose a new technique to significantly improve both the strength and toughness of C/Cs by incorporating 2D ribbon-shaped nanofillers. Silicon nitride nanoribbons (SiNNRs) are assembled into a film-like structure and inserted into each layer of a carbon fiber laminate, which is then densified with a pyrocarbon matrix. Due to the large interfacial contact area between the nanoribbon and matrix, ribbon-shaped SiNNRs can efficiently arrest and deflect cracks in both two and three dimensions, exhibiting a higher reinforcement efficiency than that of slender silicon nitride nanowires (SiNNWs). Mechanical tests show that the percentage increases in fracture toughness, flexural strength, and compressive strength of C/Cs produced by SiNNRs are approximately 9.8, 1.8, and 1.25 times higher than those produced by SiNNWs at the same volume fraction of nanofillers, respectively. This study suggests that 2D ribbon-shaped nanofillers are more effective than 1D fibrous nanofillers in enhancing the strength and toughness of C/Cs. : [Display omitted] [ABSTRACT FROM AUTHOR]

• An exceptionally strong and ductile BMGC was obtained by imitating the architecture of porcupine fish spine. • The strength-ductility synergy was due to asynchronous deformation arising from amorphous skeleton and crystalline matrix. • Bioinspired BMGC was prepared using laser additive manufacturing combined with rapid solidification technology. Introducing soft crystalline phases into the glassy matrix to produce bulk metallic glass composites (BMGCs) is an effective way to enhance the ductility of bulk metallic glasses (BMGs). However, the introduction of soft crystalline phases severely sacrifices the strength, resulting in the strength-ductility trade-off. To defeat this dilemma, here, we successfully fabricate a bioinspired BMGC with architecture mimicking a porcupine fish spine. The bioinspired BMGC shows a pronounced yield strength of ∼800 MPa with an excellent fracture strain of ∼35 %. The fabrication of the bioinspired BMGC is achieved through infiltration and vitrification of molten Zr 50 Ti 5 Cu 27 Ni 10 Al 8 (Zr50) melt into the crystalline Nb skeleton fabricated by laser additive manufacturing (LAM). Such enhanced strength-ductility synergy is attributed to the asynchronous deformation associated with the delicate bioinspired heterogeneous architecture. The bioinspired structural design motif, enabled by the combination of LAM and infiltration casting technologies, opens a new window to develop high-performance BMGCs on a large scale for structural applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• A large number (10.0 vol.%) of galvanic couples were formed ((α-Mg-Li)-Mg 2 (Ni, Cu) in designed Mg-Li-Ni-Cu alloy, with a potential difference of ∼500 mV, which is significantly higher than that of most couples formed in comparative Mg alloys. • A superb degradation rate of 2404.3 ± 24.0 mm/y was obtained, 2.3 times higher than the reported highest degradation rate of comparative Mg alloys. • Adding Ni and Cu and the formation of the Mg 2 (Ni, Cu) phase can refine the grains (1.5 μm), leading to high strength and plasticity. • The designed alloy exhibits a combined superb degradation rate (2404.3 mm/y) high compressive strength (484.9 MPa), lower density (1.70 g/cm3) and high compressive strain (16.1%). Lightweight Mg alloys with high degradation rates and high strength are attractive for fracturing tools used in unconventional oil/gas extraction. The common design strategy for such alloys is to directly add Ni/Cu into existing high-strength Mg alloys, which meets the high-strength demand but the degradation rates are still insufficient for some extreme downhole environments, especially those with low temperature and low chloride ion concentrations. Here we designed an extruded lightweight Mg-Li-Ni-Cu alloy with superb degradation rate and high strength. The high degradation rate is attributed mainly to the formation of highly effective galvanic couples, Ni/Cu-containing second phases (cathode) and Mg-Li matrix (anode) with ultrahigh potential difference. The degradation rate achieved 2404.3 mm/y, ∼2.3 times higher than the reported highest rate of extruded Mg alloys for fracturing tools. The alloy also has a high compressive strength of 484.9 MPa, which can be attributed largely to grain refinement strengthening. [ABSTRACT FROM AUTHOR]

• During deformation, stress gradients in CrCoNi alloys lead to the formation of unique inverse dislocation pileups. This is due to elevated lattice friction and stress gradients in the material. • Lowering temperature, increasing loading rates, and introducing chemical ordering promote the formation of these inverse pileups. • Inverse pileups play a crucial role in suppressing dislocation movement, reducing damage at grain boundaries, and mitigating the risk of catastrophic failure. • Dislocation mechanics analysis reveals that dislocation hardening is the dominant factor in plastic deformation of CrCoNi, even when a linear stress gradient is present, with grain boundary strengthening having a limited effect. In this work, we utilize atomistic simulations and dislocation mechanics to explore the formation of inverse pileups in CrCoNi model alloys and elucidate their unique impact on the strength and ductility of multi-principal element alloys (MPEAs). The present atomistic simulations on single crystals reveal that during the deformation of CrCoNi, stress gradients lead to the formation of novel inverse dislocation pileup. We find that this unique dislocation pattern in a confined volume is due to the elevated lattice friction and significant stress gradient present in the material. Furthermore, this phenomenon can be notably promoted by lowering the temperature, increasing the loading rate, and introducing chemical short-range ordering. Additional simulations on bicrystals show that these inverse pileups play a critical role in suppressing dislocation transmission, reflection, and grain boundary (GB) migration. As a result, they effectively mitigate stress concentration and reduce damage accumulation at GBs, lowering the risk of catastrophic failure due to GB damages. In our theoretical analysis, we utilize dislocation mechanics to predict the formation of the inverse pileup and its subsequent strengthening effect, considering scenarios with and without obstacles. Our investigations encompass various lattice frictions and stress gradients. Remarkably, our results shed light on the prevailing impact of dislocation hardening in the plastic deformation of CrCoNi even under the presence of a linear stress gradient, while the contribution of GB strengthening is found to be comparatively limited. These findings provide valuable insights into the deformation mechanisms of MPEAs in general and significantly aid their applications as promising structural materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel spheroidized + recrystallized strategy to strengthen-plasticize brittle CoCrFeNi 2 (V 6 B 3 Si) 0.149 EHEA was proposed. • A well-designed microstructure with spherical M 3 B 2 phase + fine FCC grain duplex phases was obtained. • The resulting microstructure improved YS and EL % by 48∼126 and 539 %–878 %. • The synergistic increment in strength and ductility exceeds all reported EHEAs. Eutectic high-entropy alloys (EHEAs), as a classification of high-entropy alloys (HEAs), have received worldwide interest due to superior fluidity and attractive properties. However, other than the FCC + B2 EHEA system, most other reported EHEA systems show inherent brittleness during tensile loading at room temperature, which limits their advanced engineering application. In this work, a novel spheroidization + recrystallization (SR) strategy for synergistic strengthening and plasticizing of the brittle CoCrFeNi 2 (V 6 B 3 Si) 0.149 was proposed. The superior combination of strength and ductility was achieved by tailoring spherical M 3 B 2 + recrystallized FCC duplex phases. Based on this strategy, the yield strength and elongation were improved from 565 ± 15 MPa and 2.3 % ± 0.3 % to 841 ± 24 – 1278 ± 20 MPa and 14.7 % ± 0.5 % – 22.5 % ± 1.2 %, with an increase of 48 %–126 % and 539 %–878 %, respectively. The synergistic increment in the strength and ductility of SR-FCC+M 3 B 2 EHEAs exceeds all reported further strengthened FCC + B2 EHEAs. Meanwhile, such simple thermo-mechanical processing is suitable for large-scale industrial production. The high strength results from the back stress provided by the dual heterogeneity of FCC grain sizes and soft FCC/hard M 3 B 2. The good ductility is attributed to the dislocation movement path released by spheroidized M 3 B 2 and a more uniform stress distribution caused by the recrystallized FCC. This work provides a new strategy for synergistic strengthening and plasticizing of the brittle EHEAs to meet industrial reliability requirements. [Display omitted] [ABSTRACT FROM AUTHOR]

• Thermal stabilizing and toughening of a dual-phase Nb alloy are achieved by tuning stabilizing element C in Nb-BCC. • The 3.1 % lattice expansion resulting from the BCC-to-FCC transformation compensates for the lattice relaxation induced by the precipitation of interstitial C atoms from the BCC matrix. • The exceptional performances can be attributed to the network skeletal structure of discontinuous carbide GBs and the presence of BCC+FCC dual-phase grains (K-S relationship). • The discontinuous carbide GBs can impede grain growth, block and transfer dislocations, and mediate localized deformation. Niobium alloys have found extensive application in industries, such as aerospace, nuclear reactor, and emerging electronic technologies, owing to their high melting point, low density, and remarkable formability. Nevertheless, they still fall short in terms of comprehensive strength, toughness, and thermal stability when subjected to complex impacts and/or torsional forces during service. Here, a dual-phase (BCC/FCC) Nb alloy with attractive mechanical properties and thermal stability was designed by tuning stable element C in the Nb-BCC matrix assisted by hot deformation and aging processes. Our findings reveal that the formation of discontinuous carbides at the grain boundary promotes the phase transformation of the matrix from BCC to FCC (K-S orientation relationship), resulting in the formation of FCC thin layers and nano particles. This unique configuration hinders the slipping of dislocations during deformation and impedes the degeneration of microstructures during the thermal cycling process from 200 °C to 900 °C. Moreover, the discontinuous carbides at GBs provide channels to transfer dislocations between various phases and/or grains, which results in attractive mechanical properties and thermal stability. The ultimate tensile strength, yield strength, elongation, and elasticity modulus of the designed Nb alloy reach impressive values of 790.5 MPa, 436.5 MPa, 39.1 %, and 63.5 MPa, respectively. These observations provide guidelines for designing dual-phase Nb alloys with remarkable strength, toughness, and thermal stability for aerospace applications by tuning the stabilizing element C in the Nb-BCC matrix. [Display omitted] [ABSTRACT FROM AUTHOR]

• A gradient nanograined dual-phase structure was produced in 2101 duplex stainless steel. • A superior combination of strength and ductility was achieved by superposition of gradient nanostructure and lamellar dual-phase structure. • Strong hetero-deformation induced strengthening and hardening effect contributes to the superior mechanical properties. Similar to other metallic materials, duplex stainless steel dramatically loses its advantage of high ductility as they are strengthened. Here, we produce a gradient nanograined dual-phase structure in the 2101 duplex stainless steel, thus facilitating a superior strength-ductility synergy: a yield strength of 1009.5 MPa being two times higher than that of the as-received sample, a total elongation of 23.4% and a uniform elongation of 5.9%. This novel structure is produced through a processing route of ultrasonic severe surface rolling and annealing, which realizes a superposition of gradient nanostructure and lamellar dual-phase structure with austenite and ferrite. During the tension deformation of gradient nanograined dual-phase structured duplex stainless steel, a significant accumulation of geometrically necessary dislocations occurs. These dislocations are formed to accommodate the deformation incompatibility caused by the layer-by-layer difference in strength and hardness of individual phase domains, as well as the inherent difference in properties between the austenite and ferrite domains. This results in a stronger hetero-deformation induced strengthening and hardening significantly contributing to superior mechanical properties. Our study provides a new avenue to develop advanced steels with high strength and ductility. [Display omitted] [ABSTRACT FROM AUTHOR]

Older adult consumers need easy access to packaging contents through their closure mechanisms. We propose design requirements to make a product more inclusive of older adult users by providing useful packaging design guidelines for easier usage by senior citizens. We examined packaging-versus-consumer interaction in opening procedures for 50 varied consumer products in the Japanese market. The experiment comprised observational analysis and objective and subjective assessments of 48 young and older adult users of both genders. Senior users preferred firm, compact, familiar, and light packaging with intuitive closure and an uncomplicated grip. These results may aid manufacturers in producing more universally friendly closure mechanisms. [ABSTRACT FROM AUTHOR]

Copyright of Cement & Concrete World / Cimento ve Beton Dunyasi is the property of Cimento ve Beton Dunyasi / Cement & Concrete World and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• New material constant IDS is proposed to evaluate dislocation stability and mobility. • Intrinsic mechanism of strength-plasticity restriction is tightly related to IDS. • Reduce IDS can be a criterion for synchronous improvement of strength and plasticity. In this study, the possible relationships between strength and plasticity are explored on the basis of the stability and mobility of dislocations. An independent dislocation space (IDS) model is proposed by molecular simulation of pilling-up and annihilation behaviors of screw dislocations in face-centered cubic (fcc) metals. It is revealed that there is an intrinsic driving mechanism for the restrictive strength–plasticity relation, and then the criterion for the synchronous improvement of strength and plasticity (SISP) in dislocation mechanism dominated fcc metals is proposed in terms of the IDS model. Finally, the IDS model has been verified in various practical cases and could help design high-performance metallic materials in future. [ABSTRACT FROM AUTHOR]

• A multi-scaled heterostructure from sample to atomic scales is built by TCC and blocky annealing. • Different sample positions and various regions at each position coordinate deformation. • Dense twins and twin-twin network result in significant strengthening and hardening. Compositionally-complex alloys (CCAs) with the face-centered cubic (fcc) structure exhibit excellent fracture toughness and stable mechanical property across a broad temperature range from cryogenic to room temperatures. However, yield strength of those alloys is usually low, making them difficult to meet the demands of practical engineering application. In a prototype CCA with the nominal chemical composition of Co 10 Cr 10 Fe 49 Mn 30 N 1 (atom percent), a multi-scaled heterostructure from sample to atomic scales was obtained by performing triaxial cyclic compression and short-term annealing on the blocky alloy. The material exhibits a heterogeneous distribution of strain at the sample scale. At the grain scale, dense twins and twin–twin network, laths featured with local chemical order as well as dislocation cells jointly hinder plastic deformation. At the nanoscale, the chemical order within grains also impedes dislocation motion. During plastic deformation, different sample positions within the heterogeneous material and various regions at each position undergo coordinated deformation, resulting in significant hetero-deformation induced strengthening. Simultaneously, the continuously activated dislocations, stacking faults and nano-twins lead to a high yield strength of 1020 MPa in the material while maintaining a fracture elongation of 30 %. This study provides new insights for the design and development of high-performance metallic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• A cobalt-free ODS FeCrNi MEA was fabricated by powder metallurgy method. • Nanoscale oxides are in-situ introduced into the FCC matrix. • The alloy exhibits high yield strength of 1120 MPa and 701 MPa at 25 °C and 600 °C, respectively. • The alloy shows high irradiation-induced segregation resistance. • Highly dispersed oxide nanoparticles are responsible for the high strength and outstanding irradiation resistance. A novel cobalt-free oxide dispersion strengthened (ODS) equiatomic FeCrNi medium entropy alloy (MEA) was successfully fabricated through mechanical alloying and hot extrusion (HE). The ODS FeCrNi MEA is composed of a single face-centered cubic (FCC) matrix, in which highly dispersed oxide nanoparticles, including Y 2 Ti 2 O 7 , Y 2 TiO 5 and Y 2 O 3 , are uniformly distributed. Compared with the FeCrNi MEA, the ODS FeCrNi MEA exhibits the improved yield strength (1120 MPa) and ultimate tensile strength (1274 MPa) with adequate ductility retention (12.1%). Theoretical analysis of the strengthening mechanism indicates that the high strength is mainly attributed to the grain-boundary strengthening caused by fine grains and the precipitation strengthening resulted from the oxide nanoparticles. Meanwhile, the matrix that easily activates mechanical twinning during the deformation process is the main reason to ensure moderate ductility. In addition, the introduction of high-density oxide nanoparticles can disperse the defect distribution and suppress the defect growth and irradiation-induced segregation, leading to the excellent irradiation resistance. These findings provide innovative guidance for the development of high-performance structural materials for future nuclear energy applications with balanced strength and ductility. [Display omitted] [ABSTRACT FROM AUTHOR]

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• Mg-Ti composite fabricated by infiltrating Mg melt into 3-D printed Ti scaffold. • Mg and Ti phases are topologically bi-continuous and interspersed in 3-D space. • Partially degradable implant combining mechanical durability and bioactivity. • Higher strength than Ti scaffold and pure Mg with lower modulus than dense Ti. • Non-cytotoxic, no obvious adverse reactions, and promoting new bone ingrowth. Mg (and Mg alloys) and Ti (and Ti alloys) are two important classes of metallic implant materials which are respectively completely degradable and non-degradable after implantation. Making composites composed of them offers the promise for combining their property advantages for bone repair. Here, we present a Mg-Ti composite fabricated by pressureless infiltration of pure Mg melt into 3D printed Ti scaffold, and demonstrate a potential of the composite for use as new partially degradable and bioactive implant materials. The composite has such architecture that the Mg and Ti phases are topologically bi-continuous and mutually interspersed in 3D space, and exhibits several advantages over its constituents, such as higher strengths than as-cast pure Mg and Ti scaffold along with lower Young's modulus than dense Ti. Additionally, the degradation of Mg phase may induce the formation and ingrowth of new bone tissues into the Ti scaffold to form mechanical interlocking between them; in this process, the Ti scaffold provides constant support and Young's modulus adaptively decreases toward that of bone. Despite the accelerated corrosion than pure Mg, the composite remains non-cytotoxic and does not cause obvious adverse reactions after implantation as revealed by in vitro and in vivo experiments. This study may offer a new possibility for combining mechanical durability and bioactivity in implant materials, and allow for customized and targeted design of the implant. [Display omitted] [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper Industry is the property of China Pulp & Paper Industry Publishing House and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• A tensile strength of ∼605 MPa and ∼10% elongation were obtained in Al–7Mg–0.3Sc–0.1Zr. • The strength-ductility synergy owes to a multi-scale heterogeneous microstructure. • While Al–7Mg–0.1Sc–0.3Zr had higher thermal stability at ≥ 400 °C than high-Sc/Zr ratio alloys. • High-content Zr atoms are helpful in enhancing precipitation and coarsening resistance of Al 3 (Sc,Zr). Microstructure and its thermal stability are critical in the development of high-performance Al–Mg alloys. Here, we attempt to tailor Al 3 (Sc,Zr) precipitates and thus microstructure characteristics to manipulate mechanical properties and microstructural stability of Al–7Mg alloys fabricated by hot extrusion combined with two-pass hard-plate rolling via changing Sc/Zr ratio. Increasing Sc/Zr ratio leads to improved strength without any loss of ductility. A strength-ductility synergy, i.e. yield strength of ∼548 MPa and ultimate tensile strength of ∼605 MPa with an impressive ductility of ∼10% elongation was achieved in the Al–7Mg–0.3Sc–0.1Zr alloy. The good strength-ductility synergy is ascribed to the multi-scale heterogeneous microstructure promoted by the high Sc/Zr ratio, i.e. a bimodal grain structure, profuse low angle grain boundaries, dispersed nano-sized Al 3 (Sc,Zr) precipitates coexisting with intragranular Mg-Zr co-clusters segregated at dislocations. Upon thermal exposure, the Al–7Mg–0.3Sc–0.1Zr alloy maintained higher hardness at below 250 °C, whereas Al–7Mg–0.2Sc–0.2Zr and Al–7Mg–0.1Sc–0.3Zr alloys exhibited higher hardness in moderate- and high-temperature range of 250–350 °C and ≥ 400 °C, respectively. Atom-probe tomography analysis illustrates that slow-diffusing Zr atoms enhance Al 3 (Sc,Zr) coarsening resistance through forming a higher-content Zr-enriched protective shell around a Sc-enriched core in Al–7Mg–0.1Sc–0.3Zr. Meanwhile, the high Zr content promotes concurrent Al 3 (Sc,Zr) precipitation during thermal exposure at high temperatures. The improved microstructural thermal stability in Al–7Mg–0.1Sc–0.3Zr alloy is further discussed in terms of the recrystallization resistance and grain growth behavior. The present study reveals the feasibility for designing high-strength and thermally stable hetero-structured Al–Mg–Sc–Zr alloys via tailoring Sc/Zr ratios for different application temperature ranges. [ABSTRACT FROM AUTHOR]

• The essential criterion was provided for the composition design of CoCrNi medium-entropy alloys (MEAs) with exceptional strength-ductility combinations. • The analysis on phase stability, deformation mechanisms and mechanical properties is combined in the essential criterion. • The optimal composition space of CoCrNi MEAs was predicted with the adoption of the essential criterion and first principles calculations. • The validity of essential criterion was proved by systematic comparison with numerous experimental data. The development of multi-principal element alloys (MPEAs, also called as high- or medium-entropy alloys, HEAs/MEAs) provides tremendous possibilities for materials innovation. However, designing MPEAs with desirable mechanical properties confronts great challenges due to their vast composition space. In this work, we provide an essential criterion to efficiently screen the CoCrNi MEAs with outstanding strength-ductility combinations. The negative Gibbs free energy difference ∆ E FCC-BCC between the face-centered cubic (FCC) and body-centered cubic (BCC) phases, the enhancement of shear modulus G and the decline of stacking fault energy (SFE) γ isf are combined as three requisites to improve the FCC phase stability, yield strength, deformation mechanisms, work-hardening ability and ductility in the criterion. The effects of chemical composition on ∆ E FCC-BCC , G and γ isf were investigated with the first principles calculations for Co x Cr 33 Ni 67- x , Co 33 Cr y Ni 67- y and Co z Cr 66- z Ni 34 (0 ≤ x, y ≤ 67 and 0 ≤ z ≤ 66) alloys. Based on the essential criterion and the calculation results, the composition space that displays the negative Gibbs free energy difference ∆ E FCC-BCC , highest shear modulus G and lowest SFE γ isf was screened with the target on the combination of high strength and excellent ductility. In this context, the optimal composition space of Co-Cr-Ni alloys was predicted as 60 at.%–67 at.% Co, 30 at.%–35 at.% Cr and 0 at.%–6 at.% Ni, which coincides well with the previous experimental evidence for Co 55 Cr 40 Ni 5 alloys. The validity of essential criterion is further proved after systematic comparison with numerous experimental data, which demonstrates that the essential criterion can provide significant guidance for the quick exploitation of strong and ductile MEAs and promote the development and application of MPEAs. [ABSTRACT FROM AUTHOR]

There is an increasing demand for materials with excellent mechanical performance for Micro-Electro-Mechanical System (MEMS) devices serving at elevated temperatures. However, how to enhance the high-temperature strength of the materials without losing their plasticity is a pending problem. Here, the Ni/Ni-W laminated composites with different monolayer thicknesses and the same ratio of the constituent layer thicknesses were fabricated successfully by using the dual-bath electrodeposition technique. The microstructure stability and tensile properties of annealed Ni/Ni-W laminated composites with different monolayer thicknesses were investigated at 400 °C. The results show that the annealed Ni0.5/Ni-W0.05 laminated composites have both high yield strength (450 MPa) and excellent elongation to failure (25.1%) at 400 °C, being superior to that of the monotonic Ni (179 MPa and 17.7%). Such a high strength of the laminated composite at 400 °C results from the contribution of the intrinsically high strength of the Ni-W layers with excellent thermal stability, the thickness-constrained effect on grain growth of Ni layers and the interface coupling effect of heterogeneous structures. The good plasticity may be derived from the heterogeneous laminated structure and the decrease in the constituent layer thickness, providing a good co-deformation ability. Basic mechanisms for the high tensile strength and good plasticity of the Ni/Ni-W laminated composites at 400 °C were analyzed theoretically. The findings reveal a potential strategy to fabricate MEMS components with excellent high-temperature tensile properties through tailoring the microstructure thermal stability and the constituent layer scale. [ABSTRACT FROM AUTHOR]

• Sc doping significantly suppressed discontinuous Ag precipitates in Cu-Ag alloys. • Sc-doping led to a 55 MPa increase in strength, with only a slight decrease in conductivity. • Sc segregation at grain boundaries inhibited the nucleation of discontinuous precipitates. • The UTS of Sc-doped samples was 1080 MPa, 205 MPa higher than that of non-doped samples. In low-Ag Cu matrix alloys, the presence of coarse discontinuous precipitates may limit strength. We demonstrated that discontinuous precipitation was suppressed, and continuous precipitation was enhanced by the doping of Cu-6 wt%Ag with Sc. A high-volume fraction of continuous precipitates, which nucleated on {111} planes, led to a 55 MPa increase in strength, with only a slight decrease in electrical conductivity. The addition of Sc inhibited the nucleation of discontinuous precipitates by causing the Sc and the Ag to co-segregate onto grain boundaries, thus forming a thin intermetallic compound layer between grains. After deformation, both discontinuous and continuous precipitates were drawn into Ag fibers. The combination of deformation strain and doping caused an increase in density and a decrease in the diameter of Ag fibers, resulting in about 205 MPa increase in doped samples when the deformation strain reached 4.9. The thinner, denser Ag fibers in the doped samples also caused higher electron scattering at interfaces, leading to electrical conductivity that was 11% IACS lower than in non-doped samples. For reference, 100% IACS (International Annealed Copper Standard) is equivalent to 1.7241 μΩ cm. [Display omitted] [ABSTRACT FROM AUTHOR]

• Pure Cu shows the UTS of 271 MPa and elongation to fracture of 43.5% without additional post-treatments. • Cold spray additive manufacturing can achieve combination of high strength and good ductility • The deposit microstructure shows a gradient nano-grain structure with bimodal size distribution. • The gradient nano-grained (GNG) structure in single splat composes the deposit microstructure. • The balance between work hardening and thermal softening determine the performance. In this work, pure Cu with excellent strength and ductility (UTS of 271 MPa, elongation to fracture of 43.5%, uniform elongation of 30%) was prepared using cold spray additive manufacturing (CSAM), realizing a breakthrough in the field. An in-depth investigation was conducted to reveal the microstructure evolution, strengthening and ductilization mechanisms of the CSAM Cu, as well as the single splats. The results show that the CSAM Cu possesses a unique heterogeneous microstructure with a bimodal grain structure and extensive infinitely circulating ring-mounted distribution of twinning. Based on the single splat observation, the entire copper particle forms a gradient nano-grained (GNG) structure after high-speed impact deposition. The GNG-structured single splat serves as a unit to build the heterogeneous microstructure with bimodal grain distribution during the successive deposition in CSAM. The results also show that CSAM can achieve synergistic strengthening and ductilization by controlling the grain refinement and dislocation density. This work provides potential for CSAM technique in manufacturing various metallic parts with the desired combination of high strength and good ductility without additional post-treatments. [ABSTRACT FROM AUTHOR]

• A novel approach is reported to produce carbon/carbon fiber composites of super bending strengths from nano diamonds and carbon fibers via a phase transformation by spark plasma sintering. • The unique "mortise and tenon structure" bestows the composite bulks with excellent mechanical properties. • The current composites possess the highest specific bending strength of all current high temperature structural materials reported so far. Carbon materials are important but find little application in bending components due to their unsatisfying bending strength (300–500 MPa). To fabricate carbon composites of high bending strength is a tough task, even using carbon fibers (CFs) structures as reinforcements. Here we report lamellar carbon composites of ultra-high bending strength (> 1.2 GPa) produced from CFs cloths coated with nano-diamond (ND) particles by spark plasma sintering (SPS). When NDs are sandwiched between CFs cloths, some ND particles penetrate into interstices between CFs. During the sintering, the ND particles are transformed into graphite onions; this transformation is associated with an active state of carbon atoms participating in the change. As a result, the carbon onions strongly bond the CFs together, helping consolidate the compacts into strong lamellar carbon composite bulks. The produced graphite onions from the NDs located at crossings of CFs tows form a robust mortise and tenon structure, which helps the bending strength of the lamellar composite from the compact of 40 wt.% NDs exceed 1.2 GPa. The as-prepared composite possesses the highest specific bending strength of all current high temperature structural materials reported so far. This work may pave a new way for high performance carbon materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• Giant strengthening in Al 0.1 CrFeCoNi by cold rolling and short-time annealing. • Al 0.1 CrFeCoNi possesses yield strength of 885 MPa and uniform elongation of 23.4%. • Ultrafine-grained structure and multiple deformation twins lead to high strength. Grain refinement usually makes the materials stronger, while ductility has a dramatic loss. Here, a superior tensile strength–ductility synergy in a fully recrystallized ultrafine-grained (UFG) Al 0.1 CrFeCoNi with abundant annealing twins was achieved by cold rolling at room temperature and short-time annealing. The microstructure characterization using electron backscattered scattering diffraction demonstrates that abundant geometrically necessary dislocations (GNDs) gather around the grain boundaries and twin boundaries after tensile deformation. Although coarse-grained (CG) samples undergo a larger plastic deformation than UFG samples, the GND density decreases with grain size ranging from UFG to CG. Transmission electron microscopy results reveal that the annealing twin boundary, which effectively hinders the dislocation slip and stores dislocation in grain interior, and the activation of multiple deformation twins are responsible for the superior strength–ductility synergy and work hardening ability. In addition, the yield strength of fully recrystallized Al 0.1 CrFeCoNi follows a Hall–Petch relationship (σ y = 24 + 676 d –1/2), where d takes into account both grain boundaries and annealing twin boundaries. The strengthening effects of grain boundaries and annealing twin boundaries were also evaluated separately. [ABSTRACT FROM AUTHOR]

• High pressure surface rolling generates a gradient microstructure in copper. • Nano- and ultrafine-scale structures develop near the surface. • Lightly deformed grains are observed at depths of 1–3 mm. • Partial recrystallization improves the combination of strength and ductility. The microstructure, hardness and tensile properties have been studied in copper processed by high pressure surface rolling (HPSR) both in the as-deformed condition and after subsequent annealing at 150 °C. It is found that a gradient structure with significant differences in the scale of microstructural features is formed by HPSR. The deformed microstructure varies from nano- and ultrafine-scale structures with a large fraction of high angle boundaries near the surface to lightly deformed grains at depths of 1–3 mm below the surface. Tensile tests of 1-mm-thick specimens demonstrate that the as-deformed material has a high strength and a low uniform elongation. Annealing at 150 °C results in partial recrystallization, which creates new through-thickness gradients. Except for the topmost layer and several bands in the adjacent layer, recrystallization is more pronounced close to the surface. The fraction recrystallized is at least 80% at depths of 60–300 µm after annealing for 960 min. The fraction recrystallized in the subsurface decreases with increasing depth, and the deformed layer at depths greater than 500 µm remains largely non-recrystallized after annealing. This partially recrystallized condition demonstrates an improved combination of strength and ductility. [ABSTRACT FROM AUTHOR]

• A heterogeneous structured Zr-2.5Nb alloys were fabricated successfully utilizing the grain size-dependent martensite transformation. • The present Zr-2.5Nb alloys manifest the highest yield strength (∼710 MPa), together with a high ultimate tensile strength (∼844 MPa) and good ductility (∼17.1%). • A model based on the grain-size-dependent critical resolved shear stress for dislocation slip and twinning has been proposed to explain the α' martensite substructures transition at a critical grain size d c = 3.3 μm. To further improve the service performance of Zr-2.5Nb alloy worked as pressure tubes in pressurized heavy water reactors, more investigation about the microstructure and thermomechanical processing route of Zr-2.5Nb alloy need to be conducted. In this work, a hetero-structured Zr-2.5Nb alloy was prepared by applying a novel technique. Microstructure analysis reveals that the alloy exhibits a grain size-dependent martensite substructure transition during post-rolling quenching. The hetero-structure consists of equiaxed primary α grains and the lamellae groups containing both parallel α' dislocation martensite and α' twin martensite. Compared with the previously reported Zr-Nb alloys, the present Zr-2.5Nb alloys manifest the highest yield strength (∼710 MPa), together with a high ultimate tensile strength (∼844 MPa) and good ductility (∼17.1%). The enhanced mechanical properties are found to arise from the properly controlled fraction/size of the two types of martensite, which not only significantly strengthens the alloy but also contributes to a stronger strain hardening. A model based on the grain-size-dependent critical resolved shear stress for dislocation slip and twinning has been proposed to explain the α' martensite substructures transition at a critical grain size d c = 3.3 μm. Below this size, the critical resolved shear stress (CRSS) for twinning is higher than that for the slip. Thus, the α' dislocation martensite is more favorable to form. Otherwise, the α' twin martensite would exhibit a high activity. The present work indicates that making use of the grain size-dependent martensite transformation to tailor the hetero-structure in Zr alloys is an effective strategy to overcome the strength–ductility trade-off in the material. [Display omitted] [ABSTRACT FROM AUTHOR]

• The microstructure of nacre is coordinated with its macroscopic shell morphology. • A hierarchical crack-bridging model is proposed to predict the strength and toughness of nacre. • T-stress effect is coupled with the wavy morphology of mineral platelets and significantly amplifies the mechanical properties of nacre. Through long-term evolution, biological tissues have optimized their components and structures at multiple length scales to meet the requirements of mechanical properties and biological functions. In this study, we explore how the shell macrostructure of nacre and its brick–mortar microstructure are synergistically designed to adapt to external mechanical conditions. We found that the T-stress effect plays a key role in linking the high toughness of nacre with its hierarchical microstructure. When an abalone shell with a convex morphology is subjected to an impact load from a predator, a compressive T-stress arises with the crack initiating in the macroscale nacreous shell. A hierarchical crack bridging model is presented to investigate how the T-stress affects the microscopic stress transfer mechanism and the macroscopic mechanical properties of nacre. It is found that the negative T-stress enhances the interfacial stress of the mineral platelet with waviness, a typical secondary structural feature of the brick–mortar structure. In turn, the amplified interfacial stress further leads to a significant increase in the macroscopic strength and fracture toughness of nacre. This work not only reports a novel toughening mechanism resulting from the structural hierarchy of nacre, but also provides inspirations for the design of biomimetic composite structures with enhanced mechanical properties. A hierarchical crack-bridging model is developed to elucidate the effects of T-stresses on the macroscopic strength, fracture toughness, and crack sensitivity of nacre. [Display omitted] [ABSTRACT FROM AUTHOR]

• P. tricuspidata tendril is a mechanically robust design with multiple functions. • High robustness, load-bearing capability, and efficiency are simultaneously achieved. • The tendrils form a narrowing configuration and their main axes take a zigzag shape. • Experimental, theoretical, and numerical efforts are combined to reveal the mechanism. Through an array of spatially distributed tendril pads, Parthenocissus tricuspidata adheres itself firmly to the surfaces of targets such as trees and walls. The tendril pads, which form unique and intriguing layouts, play a critical role in supporting plant organs. However, the relationship between their geometric forms and mechanical properties remains inadequately understood. In this paper, we combine experimental measurement, theoretical analysis, and numerical simulation to decipher the morphomechanics of P. tricuspidata tendrils. The structural geometry and load-bearing capability of the tendrils were measured. A structural mechanics model, supported by finite element simulations, is proposed to analyze the properties of different tendril layouts. The results show that the gradually narrowing distribution of the pads and the zigzag pattern of the main axis synergistically make the tendrils a comprehensively excellent mechanical design. The tendrils can simultaneously achieve superb mechanical robustness, outstanding load-bearing capability, and high efficiency of material usage. We develop an optimization method, and find that the optimized tendril layout is similar to the real one. It is also revealed that the real pad distribution renders a flaw-insensitive design. As their branchlets or pads are partly broken, the tendrils can still effectively accommodate external forces in different directions, and their structural stiffnesses do not change significantly. This work not only deepens our understanding of the structure–property–function interrelations of P. tricuspidata tendrils, but also provides inspirations for the design of, e.g., high-performance suspended cables. [Display omitted] [ABSTRACT FROM AUTHOR]

Assessing the comprehensive strength of structures under multiple loading conditions is crucial for designing microstructures. This paper proposes the use of the least failure energy density (LFED) to measure the comprehensive strength of heterogeneous periodic structures, which corresponds to the minimum energy density required to destroy a structure. To enhance the comprehensive strength of a periodic structure, the LFED can be maximized. We constructed a two-layer optimization algorithm and found that the high time consumption renders topology optimization unfeasible. We subsequently developed an approach for solving inner-layer optimization analytically and quickly so that the problem becomes a single-layer optimization. We compared the LFED of several classical structures, including plate structures, lattice structures, and TPMSs. The calculations reveal that plate structures exhibit the best performance in terms of LFED, followed by TPMSs whereas truss structures have the poorest performance. Among the three types of classical structures, the octet plate, Schwartz-D minimal surface, and octet truss structures are the best-performing types, respectively. Additionally, the LFED is combined with the BESO topology optimization method to obtain the best 2D periodical structure, a 2D curved-edge kagome structure. For optimal 3D periodical structures, rarely discussed space kagome structures (plate or lattice) are obtained with an LFED superior to that of other counterpart classical structures. [ABSTRACT FROM AUTHOR]

We investigate the conditions for crack nucleation in variational gradient damage models used as phase-field models of brittle and cohesive fracture. Viewing crack nucleation as a structural stability problem, we analyze how solutions with diffuse damage become unstable and bifurcate towards localized states, representing the smeared version of cracks. We consider gradient damage models with a linear softening response, incorporating distinct softening parameters for the spherical and deviatoric modes. These parameters are employed to adjust the peak pressure and shear stress, resulting in an equivalent cohesive behavior. Through analytical and numerical second-order stability and bifurcation analyses, we characterize the crack nucleation conditions in quasi-static, rate-independent evolutions governed by a local energy minimization principle. We assess the stability of crack development, determining whether it is preceded by a stable phase with diffuse damage or not. Our results quantitatively characterize the classical transition between brittle and cohesive-like behaviors. A fully analytical solution for a one-dimensional problem provides a clear illustration of the complex bifurcation and instability phenomena, underpinning their connection with classical energetic arguments. The stability analysis under multi-axial loading reveals a fundamental non-trivial influence of the loading mode on the critical load for crack nucleation. We show that volumetric-dominated deformation mode can remain stable in the softening regime, thus delaying crack nucleation after the peak stress. This feature depends only on the properties of the local response of the material and is insensitive to structural scale effects. Our findings disclose the subtle interplay among the regularization length, the material's cohesive length-scale, structural size, and the loading mode to determine the crack nucleation conditions and the effective strength of phase-field models of fracture. [ABSTRACT FROM AUTHOR]

• The effects low-temperature retrogression and re-aging treatments on the strength and electrical conductivity of 7050 aluminium alloy plate were studied. • Low retrogression temperature can delay or slow down precipitation and growth of precipitates, and help prolonging the retrogression times to more than ten hours. • Balancing strength and corrosion resistance (electrical conductivity) needs integrated optimization of microstructure and aging processes. The retrogression and re-aging (RRA) processes, aimed mainly at tailoring intergranular precipitates, could significantly improve the corrosion resistance (i.e., stress corrosion cracking resistance) without considerably decreasing the strength, which signifies that an efficient control of the size, distribution and evolution of intergranular and intragranular precipitates becomes critical for the integrated properties of the (mid-)thick high-strength Al alloy plates. Compared to RRA process with retrogression at 200 °C (T77), this study investigated the impact of a modified RRA process (MT77) with lower retrogression temperatures (155-175 °C) and first-stage under-aging on the properties of a high-strength AA7050 Al alloy, in combination with detailed precipitate characterization. The study showed that the strength/microhardness of the RRA-treated alloys decreased with raising retrogression temperature and/or prolonging retrogression time, along with the increased electrical conductivity. The rapid responsiveness of microstructure/property typical of retrogression at 200 °C was obviously postponed or decreased by using MT77 process with longer retrogression time that was more suitable for treating the (mid-)thick plates. On the other hand, higher retrogression temperature facilitated more intragranular η precipitates, coarse intergranular precipitates and wide precipitate free zones, which prominently increased the electrical conductivity alongside a considerable strength loss as compared to the MT77-treated alloys. With the preferred MT77 process, the high strength approaching T6 level as well as good corrosion resistance was achieved. However, though a relatively homogeneous through-thickness strength was obtained, some small discrepancies of properties between the central and surface areas of an 86-mm thick 7050 Al alloy plate were observed, possibly related to the quenching sensitivity. The precipitate evolution and mechanistic connection to the properties were discussed and reviewed for high-strength Al alloys along with suggestions for further RRA optimization. [ABSTRACT FROM AUTHOR]

• Defects of additive manufactured ceramic were characterized by X-CT. • Effects of solid loading on defects were studied. • Formation mechanism of defects in SL additive manufactured ceramics is revealed. • Intrinsic relationship between defects and mechanical properties is revealed. Ceramics have been widely fabricated by additive manufacturing (AM). Compared to conventional technologies, the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process. These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics. However, systematic research on defects, including defect geometrical features, quantitative statistics, and formation mechanism, as well as the intrinsic relationship with mechanical properties, need to be studied in depth. In this work, Al 2 O 3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic (SL) additive manufacturing. The defects, including their sizes and distributions, in both green and sintered bodies were investigated by using scanning electron microscopy (SEM) and X-ray computed tomography (X-CT). Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism. Moreover, the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed. This study can give some fundamental understanding of the defects in additive manufactured ceramics. [Display omitted]. [ABSTRACT FROM AUTHOR]

• Bulk nanocrystalline W-Ti alloys were prepared by high-pressure consolidation. • Hardness and yield strength of bulk nanocrystalline W 80 Ti 20 are 16.9 and 6.0 GPa. • High hardness and strength are mainly caused by grain boundary strengthening. • Nanocrystalline W 80 Ti 20 is stable against high temperature and deformation. • Segregation of Ti at grain boundaries makes nanocrystalline W 80 Ti 20 stable. Nanocrystalline (NC) W metals and alloys often exhibit higher radiation tolerance and strength than their coarse-grained counterparts. However, their thermal stability is low, making it difficult to achieve bulk NC W metals and alloys by consolidation using conventional techniques such as pressure-less sintering, hot-explosive-compaction sintering, and spark plasma sintering. Here we report the synthesis and mechanical properties of bulk NC W 100- x Ti x (x = 10 at.%–30 at.%) alloys prepared by consolidating mechanically alloyed NC powders under a high-temperature/high-pressure condition. Adding 20 at.%–30 at.% Ti largely improves the sinterability of NC W-Ti alloy powders. The room-temperature microhardness and compressive yield strength of consolidated bulk NC W 80 Ti 20 alloy are ∼ 16.9 and 6.0 GPa, respectively, which are mainly caused by grain boundary strengthening and significantly higher than those of previously reported W and W alloys. The ultimate compressive strength of bulk NC W 80 Ti 20 measured between 900 and 1100 °C deceases with increasing temperature. This behavior can be explained by the activation of Rachinger grain boundary sliding. No grain growth is observed in bulk NC W 80 Ti 20 after compression at 1000 °C. Theoretical calculation suggests that it is the segregation of Ti at grain boundaries that decreases the specific grain boundary free energy and makes the NC W 80 Ti 20 alloy thermodynamically stable. [ABSTRACT FROM AUTHOR]

A very coarse-grained (335 μm) Fe 41 Mn 25 Ni 24 Co 8 Cr 2 high-entropy alloy with a single FCC phase was cold rolling to a 80% reduction in thickness using the differential speed rolling technique with various speed ratios (SRs) ranging between 1 and 4. As the SR was increased, the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear strain. At SR = 4, the entire thickness of the sheet was covered with micro-shear bands, and ultrafine (sub)grains with a size of 1.4 μm were uniformly formed along the shear bands. A continuous dynamic recrystallization (CDRX) mechanism occurred during rolling, and a higher SR accelerated the CDRX process. During conventional rolling (at SR=1), a brass { 110 } 〈 112 〉 orientation texture with minor components of S { 123 } 〈 634 〉 and Cu { 112 } 〈 111 〉 orientations developed. At higher SRs, shear texture developed as the main type, while the development of rolling texture was suppressed. The microstructure at SR=4 obtained after annealing at 973 K showed a fully recrystallized microstructure composed of a five times smaller grain size (4 μm) with a higher intensity of γ fiber texture compared with that prepared by conventional rolling. The samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after annealing. The current results demonstrate that by using differential speed rolling with a high SR, one can achieve a significantly finer and more homogeneous microstructure, stronger shear texture, and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional rolling. The strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening. [ABSTRACT FROM AUTHOR]

• Segregation of solid solutes in ZrC grain boundaries are studied by first-principles. • The segregation is dominated by atomic size effect. • Segregation energy can be predicted by machine learning method. • ZrC grain boundaries can be strengthened by segregation of smaller atoms. • Strengthening grain boundaries can improve high temperature strengths of ZrC. ZrC is a promising candidate for the application in ultra-high temperature regime due to its unique combination of excellent properties, such as high melting point, good chemical inertness and high temperature stability. The rapid decrease of strength at high temperatures, however, is one of the obstacles that impedes its practical services. Strengthening of grain boundaries by solute segregation is believed to be an effective way to improve its high temperature performance. Therefore, the segregation tendency of ten solid solute atoms, including Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W, in ZrC grain boundaries, and the strengthening/weakening effects on grain boundaries due to segregation are investigated by first-principles calculations. The segregation tendency is found dominated by the size effect, which is confirmed by both a qualitative analysis and a quantitative approach based on support vector regression. It means that big atoms tend to segregate to grain boundary sites with local expansions, while small atoms tend to segregate to grain boundary sites with local compressions. Simulations on stress-strain responses indicate that segregation of small atoms (Ti, V, Cr, Nb, Ta, Mo, W) can usually improve grain boundary strengths by inducing compression strains to grain boundaries, even though there is also an exception. In contrast, segregation of Sc and Y will soften grain boundaries. The results reveal that strengthening of grain boundaries by solute segregation is a valuable avenue to enhance high temperature mechanical properties of ZrC, providing guidelines for further design of ZrC based materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• A face-centered cubic single-phase FeCrNi medium entropy alloy with a high Cr (~35 at.%) content was successfully manufactured by selective laser melting (SLM). • This as-SLMed MEA presents a hierarchical microstructure of coarse columnar grains and submicron cell structures. Cr, and also interstitial C , are found segregated to the cell boundaries. • The as-SLMed FeCrNi MEA shows a good combination of strength (σ0.2 = 745 MPa, σUTS=1007 MPa) and ductility (εf=31%), as well as a superb corrosion resistance (i corr =0.06 μA/cm2). Selective laser melting (SLM) has the advantage in preparing supersaturated solid solutions due to its unique thermal field and high solidification rate. In this study, a face-centered cubic single-phase FeCrNi medium entropy alloy (MEA) with an ultrahigh Cr content (~35 at.%) was additively manufactured by SLM. The as-built MEA shows a hierarchical microstructure of coarse columnar grains and submicron dislocation cell structures, where the cell boundaries are probed segregated with Cr and C and decorated with nano carbides. The appearance of these dislocation barriers results in an excellent combination of strength (σ 0.2 =745 MPa, σ UTS =1007 MPa) and ductility (ε f =31%). The current MEA also shows a superb corrosion resistance with a corrosion current density of 0.06 μA cm−2 in 3.5 wt.% NaCl solution, which is far lower than that of 316 L. The high content of solutioned Cr in the MEA ensures sufficient Cr supply to form an integrated Cr 2 O 3 passive film, and the large number of cell boundaries acting as the diffusion channels lead to the fast formation of a stable passive film over the alloy surface. [Display omitted] [ABSTRACT FROM AUTHOR]

• A strongest (4.1 GPa) medium carbon ferrite-pearlite steel wire is produced. • Microstructural evolution and parameters with drawing strains are quantified. • Strengthening mechanisms of medium carbon ferrite-pearlite steel are identified. • Good agreement between estimated and measured flow stresses is found. • Rule of mixture works based on quantified microstructural parameters with strain. Via traditional wire drawing, the medium carbon ferrite-pearlite (MCFP) steel wires can achieve the ultrahigh strength beyond 4 GPa normally for high-carbon pearlitic steel wires, but have a 30–60% lower production cost. The microstructural evolution and mechanical properties of medium carbon ferrite-pearlite steel wires have been investigated by means of scanning electron microscopy, transmission electron microscopy and tensile testing. The tensile strength of medium carbon ferrite-pearlite steel wires increases from 750 MPa up to 4120 MPa when the drawing strain increases up to ε = 6.4, which represents the highest strength reported so far – to our knowledge for a carbon steel with such low carbon content. At low and medium strains (ε ≤ 1.95), the proeutectoid ferrite forms dense dislocation walls (DDWs) via dislocation activities, including sliding, accumulation, interaction, and tangling. With the drawing strain increase, the reorientation of DDWs to the drawing direction forms the coarse proeutectoid ferrite lamellae. Finally, the proeutectoid ferrite deformed to high strains is characterized by a lamellar morphology and the average lamellar spacing of proeutectoid ferrite is about 55 nm at ε = 6.4. The interlamellar spacing of pearlite and thickness of cementite decreases with the drawing strain increases. The dislocation density in ferrite lamellae increases with the drawing strain increases, and the dislocation density in ferrite lamellae is 7.8 × 1015 m−2 at ε = 4.19. A higher dislocation density of 3.1 × 1016 m−2 can be obtained at ε = 6.4 by means of extrapolation and TEM investigations. The stress contributions of proeutectoid ferrite and pearlite to the flow stress are estimated based on quantified structural parameters. Based on the assumption that the stress contributions from different strengthening mechanisms are linearly additive and the general rule of mixtures, a good agreement between the measured and estimated flow stresses has been found in a large range of flow stress. The good application of the general rule of mixture to the medium carbon ferrite-pearlite steel wires indicates the importance of quantitative characterization of microstructural evolution and parameters with the strain. [Display omitted] [ABSTRACT FROM AUTHOR]

• Sc clusters with a high number density were produced in Al-Sc alloy aged at 250 °C. • The evolution of Sc clusters with aging time was characterized by APT. • The Sc solute cluster could promote strength-ductility synergy in Al-Sc alloy. • The effect of clusters on ductility is discussed by a revised micromechanics model. Sc solute clusters with a high number density were produced in an Al-0.3 wt.% Sc alloy when aged at 250 °C, while fine Al 3 Sc precipitates were predominantly formed in the same alloy aged at 300 °C. The alloy strengthened by Sc solute clusters displayed higher yield strength and simultaneously greater ductility than its counterpart strengthened by Al 3 Sc precipitates. This clearly demonstrates a superior strength-ductility synergy promoted by the Sc solute clusters in Al-Sc alloys. The effects of Al 3 Sc precipitates and Sc solute clusters on ductility were discussed in comparison by using a micromechanics fracture model. Since the Sc clusters were stabilized at 250 °C, the Al-Sc alloys strengthened by Sc solute clusters should find extensive application fields within a wide temperature range, due to their high temperature resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

In order to construct quasi-continuously networked reinforcement in titanium (Ti) matrix composites, in this study, Ti-6Al-4V spherical powders were uniformly coated with a graphene nanosheet (GNS) layer by high energy ball milling and then consolidated by spark plasma sintering. Results showed that the GNS layer on the powder surface inhibited continuous metallurgy bonding between powders during sintering, which led to the formation of quasi-networked hybrid reinforcement structure consisting of in-situ TiC and remained GNSs. The networked GNSs/Ti64 composite possessed noticeably higher tensile strength but similar ductility to the Ti64 alloy, leading to both better tensile strength and ductility than the GNSs/Ti composite with randomly dispersed GNSs and TiC. The formation mechanism and the fracture mechanism of the networked hybrid reinforcement were discussed. The results provided a method to fabricate Ti matrix composites with high strength and good ductility. • Networked GNSs/Ti composite was fabricated by combination of two-step mixing and SPS. • Increment defects of GNSs would cause GNSs chemically reacting and forming TiC wall. • GNSs or TiC inhibited the powder metallurgy bond and kept a powder size of networks. • Different phase interfaces of networked GNSs/Ti64 were observed by HRTEM and STEM. • Formation mechanisms and strengthening effects of networked structure were discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

In a recent study, Kumar and Lopez-Pamies (J. Mech. Phys. Solids 150: 104359, 2021) have provided a complete quantitative explanation of the famed poker-chip experiments of Gent and Lindley (Proc. R. Soc. Lond. Ser. A 249: 195–205, 1959) on natural rubber. In a nutshell, making use of the fracture theory of Kumar, Francfort, and Lopez-Pamies (J. Mech. Phys. Solids 112: 523–551, 2018), they have shown that the nucleation of cracks in poker-chip experiments in natural rubber is governed by the strength — in particular, the hydrostatic strength — of the rubber, while the propagation of the nucleated cracks is governed by the Griffith competition between the bulk elastic energy of the rubber and its intrinsic fracture energy. The main objective of this paper is to extend the theoretical study of the poker-chip experiment by Kumar and Lopez-Pamies to synthetic elastomers that, as opposed to natural rubber: (i) may feature a hydrostatic strength that is larger than their uniaxial and biaxial tensile strengths and (i i) do not typically exhibit strain-induced crystallization. A parametric study, together with direct comparisons with recent poker-chip experiments on a silicone elastomer, show that these two different material characteristics have a profound impact on where and when cracks nucleate, as well as on where and when they propagate. In conjunction with the results put forth earlier for natural rubber, the results presented in this paper provide a complete description and explanation of the poker-chip experiments of elastomers at large. As a second objective, this paper also introduces a new fully explicit constitutive prescription for the driving force that describes the material strength in the fracture theory of Kumar, Francfort, and Lopez-Pamies. [ABSTRACT FROM AUTHOR]

Inspired by the fact that the architecture of natural biomaterials has a great influence on their mechanical properties, the present work designed a Al 2 O 3 –poly (methyl methacrylate) composite with an interlocked wood-like architecture, which can balance the contradictions between flexural strength–fracture toughness. The results shows that the mechanical performance of the composites can be tuned through the adjustment of the tilt angle of the Al 2 O 3 spiral fibres. The composite with a tilt angle of 30° exhibited the highest flexural strength and fracture toughness, showing the ability to overcome the trade-off between flexural strength and fracture toughness. All composites exhibited weak compressive strength anisotropy owing to the interlocked helical architecture in which the continuous fiber spiraled in 3D space. Toughening mechanisms including crack deflection, crack bridging, crack bifurcation, microcracking were observed. Numerous microcracks were nucleated in the Al 2 O 3 ceramic skeleton, and they propagated along the main crack under the bridging effect of poly (methyl methacrylate). All of the composites featured suture-like cracks perpendicular to the direction of the main cracks, which was a unique toughening mechanism found in this architecture. Large-size composites can be prepared through the adopted technique to meet the demands of engineering applications. [Display omitted] [ABSTRACT FROM AUTHOR]

We present a robust analytic implementation of Physical Regime Sensitivity (PRS), which quantifies sensitivity of an experiment or application to regimes of a material model's independent variables rather than to model parameters. The new PRS implementation is tested on impact-driven Richtmyer–Meshkov Instability (RMI) strength experiments on tantalum. Sequential PRS hydrocode simulations perturbed strength in local regimes of independent variables like strain rate to quantify the resulting effects on experimentally measured maximum spike velocities in the instabilities. The numeric behavior of the sensitivity calculation is investigated regarding mesh convergence and the parameters controlling the strength perturbation. The sensitivities generally converge with mesh size at least as quickly as the underlying RMI simulations. A wide range of perturbation amplitudes produced similar normalized sensitivities, indicating the perturbation is not changing physical behavior in the simulation. Adjusting the range (width) over which the strength is perturbed allows for resolving fine sensitivity features covering narrow regimes of independent variables or more broad regimes for general interpretation. For interpreting RMI, PRS shows that the maximum spike velocity of the instability is most sensitive to a narrow regime of strain rates near 1 0 7 /s, which occurs inside the spike as strength effects arrest the instability. The PRS analyses revealed that a modification to the experimental metric used to assess strength would better isolate the strength effects in the regimes of most interest. Using the new metric to generate pressure PRS curves revealed that sensitivities to strength at near-zero pressure were 3.5 times greater than at the high-pressure shock state, supporting the practice of using RMI to isolate strain rate effects when combined with high-pressure experiments. It is also shown that a simple, calibrated constant strength model can reproduce PRS sensitivities of a complex, multivariate Preston–Tonks–Wallace strength model quite well, which supports the robustness of PRS and its utility for experimental design and interpretation prior to the availability of a sophisticated material strength model. [Display omitted] • Physical Regime Sensitivity (PRS) provides insight to experimental metric sensitivity. • Implementation of PRS using an analytic form is more robust and flexible. • Confirmation of key assumption of using RMI as a low pressure strength measurement. • A new metric for RMI that better isolates deviatoric strength sensitivity. [ABSTRACT FROM AUTHOR]

Obtaining complete rock cores is exceptionally challenging in certain extreme environments, such as deep earth and deep space; consequently, it is difficult to obtain the macro strengths of rock, which are the key indexes for engineering design, via standard rock mechanical tests. This research indicates that by determining and leveraging the mechanical properties of grains and grain-to-grain interfaces, the rock macro strength can be effectively estimated. Nanoindentation tests were first conducted to determine the elastic modulus of the mineral grains and their interfaces. Subsequently, symmetrical and anti-symmetrical four-point bending tests were executed to establish the statistical law governing interfacial tensile and shear fracture toughnesses. Furthermore, by employing the Dugdale–Barenblatt model and considering the oblique angular distribution of interfacial cracks, the corresponding tensile strength, shear strength, and friction parameter were derived. These meso‑mechanical parameters were then inputted into the 3D Finite-Discrete Element Method to estimate rock macro strength. And the numerical results were then compared with the results of standard uniaxial compression, direct tension, Brazilian splitting, and direct shear tests. The consistency observed between the predictions and experimental results attests to the validity of the proposed method. [ABSTRACT FROM AUTHOR]

[Display omitted] • A family of novel Co-Ta-B-Si bulk metallic glasses (BMGs) was developed. • The BMGs exhibit both high strength above 5.5 GPa and large plasticity up to 6.4 %. • The BMGs show the enhancement of glass-forming ability (GFA: up to 4 mm). • The improvement of plasticity and GFA were explained by calculated analysis. • A self-organization behavior of shear bands is liable for the increase in plastic. Development of advanced metals materials with ultrahigh strength, large plasticity and high thermostability is one of the most attractive aims for materials researchers. Co-based bulk metallic glasses (BMGs) with the highest strength (up to 6 GPa) and special strength (up to 650 Nm/g) among all of metals materials so far we known have received extensive attentions. In this paper, a family of Co-Ta-B-Si BMGs with high glass-transition temperature (above 870 K), large compressive plasticity (up to 6.4 %) and high strength (above 5.5 GPa), and high glass-forming ability (the critical diameter, D c : up to 4 mm) was developed by accurately tuning metalloid element contents of Si and B in the parental alloy of Co 55 Ta 10 B 35. The changes of glass formation and plasticity caused by the adjustment of the constituent metalloid elements were evaluated by the combination of experimental and calculated results. The reason for the significant improvement of plastic deformation is revealed by the analysis of the self-organization behaviors of high-density shear bands. [ABSTRACT FROM AUTHOR]

• Re0.5MoNbW(TaC)0.5 composite with eutectic structure had ultra-strength at 1200 ℃. • Phase and structure remained stable after annealing at 1300 ℃ for 168 h. • Dual-phase with eutectic structure has an effective strengthening effect. • Semi-coherent interface plays a dominant in providing high strength. The dual-phase Re 0.5 MoNbW(TaC) 0.5 composite, consisting of refractory body-centered cubic (BCC) high-entropy alloy and carbide with many fine eutectic structures, was successfully synthesized by arc melting. The phase stability, high-temperature mechanical properties and strengthening mechanism of the as-cast composite were studied. The microstructure of the composite remained stable after annealing at 1300 ℃ for 168h. It exhibited remarkably high-temperature strength, yield strength ∼ 901 MPa, and true ultimate compressive strength ∼ 1186 MPa at 1200 ℃. The BCC phase and carbide exhibited a semi-coherent interface with good bonding after severe deformation at 1200 ℃. The dipolar dislocation walls in BCC phase, restricted dynamic interaction between defects in carbide, and the pinning effect of semi-coherent interface offered effective strengthening effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • SRS combined with HPR allows for a Mg-6Zn-0.2Ca alloy having a superior combination of ductility and strength. • Refined and dispersed eutectic phase introduced by SRS and HPR could effectively alleviate or avoid the crack initiation. • Excessive Ca solute atoms in α-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability. In this study, we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification (SRS) combined with hard-plate rolling (HPR), whose elongation-to-failure increases from ∼17 % to ∼23 % without sacrificing tensile strength (∼290 MPa) compared with its counterpart processed via conventional solidification (CS) followed by HPR. Notably, both samples feature a similar refined grain structure with an average grain size of ∼2.1 and ∼2.5 μm, respectively. However, the high cooling rate of ∼150 K/s introduced by SRS modified both the size and morphology of Ca 2 Mg 6 Zn 3 eutectic phase in comparison to those coarse ones under CS condition. By subsequent HPR, the Ca 2 Mg 6 Zn 3 phase was further refined and dispersed uniformly by severe fragmentation. Specially, the achieved supersaturation containing excessive Ca solute atoms due to high cooling rate was maintained in the SRS-HPR condition. The mechanisms that govern the high ductility of the SRS-HPR sample could be ascribed to following reasons. First, refined Ca 2 Mg 6 Zn 3 eutectic phase could effectively alleviate or avoid the crack initiation. Furthermore, excessive Ca solute atoms in α-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability during tension. The findings proposed a short-processed strategy towards superior performance of Mg-6Zn-0.2Ca alloy for industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic FeCo-based nanoprecipitates were introduced in FeCo-2V soft magnetic alloy by a small addition of Cr, Mo elements. • Magnetic nanoprecipitates increase the high-temperature strength while maintaining a low coercivity in FeCo-based alloy. • The characteristic of magnetic nanoprecipitates was revealed by TEM observation. Precipitation strengthening is an effective approach to enhance the strength of soft magnetic alloys for applications at high temperatures, while inevitably results in deterioration in coercivity due to the pinning effect on the domain wall movement. Here, we realize a good combination of high-temperature strength and ductility (ultimate tensile strength of 564 MPa and elongation of ∼ 20 %, respectively) as well as low coercivity (6.97 Oe) of FeCo-2V-0.3Cr-0.2Mo soft magnetic alloy through introducing high-density magnetic nanoprecipitates. The magnetic nanoprecipitates are characterized by FeCo-based phase with disordered body-centered cubic structure, which enables the alloy to have a low coercivity. In addition, these nanoprecipitates can impede the dislocation motion and suppress the brittle fracture, which lead to a high tensile strength and ductility. This work provides a guideline to enhance strength and ductility while maintaining low coercivity in soft magnetic alloys via magnetic nanoprecipitates. [ABSTRACT FROM AUTHOR]

The strength and plasticity of Fe 39 Ni 39 B 12.82 Si 2.75 Nb 2.3 P 4.13 bulk metallic glass (BMG) are improved simultaneously by modulating atomic-scale structure through fluxing treatment. The compression strength increases from 3074 to 4220 MPa, and the plastic strain is enlarged from 10.7 % to more than 50 %. The increased mechanical properties of the fluxed FeNiBSiNbP BMG originate from the optimization of atomic-scale structure. More icosahedral-like clusters (ILCs) and crystal-like clusters (CLCs) are found in this FeNi-based BMG with fluxing treatment, and the ILCs are usually surrounded by CLCs. Furthermore, phase separation and a sandwich-like heterogeneous structure of SB are also observed during deformation, indicating the multiscale deformation mechanism and a stable shear-band evolution. The unique "ILC surrounded by CLCs" structure and phase separation lead to a stable plastic deformation process with strong interactions of multiple shear bands, thereby the improved plasticity and strength. This work provides useful guidelines to develop strong and plastic Fe-based BMGs from a structural aspect. [ABSTRACT FROM AUTHOR]