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Near-equiatomic single-phase twining-induced plasticity (TWIP) high-entropy alloys (HEAs) exhibit a good combination of strength and ductility, but their modest yield strength requires further improvement. Here, we propose a strategy for markedly enhancing their strength while retaining satisfactory ductility, taking advantage of the temperature dependence of the stacking fault energy. The room-temperature strength of a representative TWIP HEA was improved by the cryogenic pre-deformation-induced dislocations, martensite, nanotwins, and stacking faults. The tensile properties were further tuned by subsequent annealing to obtain partially recovered or recrystallized microstructures. The influence of regulated microstructures on the yield strength was clarified by neutron diffraction line profile analysis. The room temperature tensile yield strength of the HEA increased from 275 to 1012 MPa while retaining an elongation of 21.9%. The yield strength and elongation were then further altered to 826.9 MPa and 42.6%. This study presents possibilities for fabricating advanced HEAs by tuning the substructures. [Display omitted] [ABSTRACT FROM AUTHOR]

The transition behavior from a Nb–Ni precursor to porous Nb and the coarsening of ligaments by a dealloying reaction in a Mg melt are investigated. Based on these results, the kinetics of the reaction are discussed. When a Nb 25 Ni 75 (at.%) disk was immersed in a Mg melt, the Ni content decreased the most at the surface of the disk and less so towards the interior of the disk. In this disk, it was found that transition layers of body-centered cubic-Nb and Ni 6 Nb 7 formed. These transition layers grew, following a parabolic law, and the activation energy of such growth was close to values reported for the diffusion of solute atoms in liquids, suggesting that diffusion of Ni in the Mg melt was the rate-controlling process of the dealloying reaction. The ligament size depended on time and temperature, following a power law with an exponent of 4, suggesting that surface diffusion was a key part of coarsening. These results agree well with those reported for conventional dealloying in an aqueous solution. Based on the kinetics analyses, the dealloying conditions were optimized to maximize the specific surface area, allowing a Nb electrolytic capacitor to be produced with a maximum mass-specific capacitance of 650,000 μFV g −1 , about three times larger than the highest value previously reported. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic calculation of elastic properties in Ti-containing, biocompatible refractory high-entropy alloys. • Modeling of non-random texture effects on poly-crystalline moduli. • Directionally preferential Young's moduli achievable in single crystals and textured poly-crystals. • Valence electron count has a dominant influence on elastic anisotropy. A high-priority target in the design of new metallic materials for load-bearing implant applications is the reduction of Young's modulus approximating that of cortical bone in the predominant loading direction. Here, we explore how directionally preferential bulk elastic properties of implant materials are achieved by harnessing elastic anisotropy. Specifically focusing on recently proposed biocompatible refractory high-entropy alloys (RHEAs) in the body-centered cubic structure, we conduct systematic density-functional theory calculations to investigate the single-crystal elastic properties of 21 Ti-containing RHEAs. Our results provide evidence that the valence electron count has a dominant influence on elastic anisotropy and crystal directions of low Young's modulus and high torsion modulus in the RHEAs. By means of modeling the orientation distribution function for crystallographic texture, we examine the effect of non-random texture on the anisotropic poly-crystalline Young's modulus and torsion modulus with varying texture sharpness. We adopt fiber textures that can result from rolling and distinct texture orientations that can form during rapid directional solidification. We discuss the potential for lowering Young's modulus in the RHEAs by using single crystals or textured aggregates. Furthermore, we prepare four of the theoretically considered alloys by arc-melting and report their lattice parameters, quasi-isotropic Young's moduli, and Wickers hardnesses. [ABSTRACT FROM AUTHOR]

Abstract: A Mg3Cu3Gd bulk metallic glass matrix composite with porous α-Ti dispersoids was prepared by dealloying in a metallic melt. The in situ formed α-Ti dispersoids had a pore-size of ∼500nm, which was imparted from the Ti2Cu precipitate in the prealloy. Pore size was therefore controllable through the cooling rate of the prealloy preparation. Plasticity was not improved apparently, however the maximum fracture stress under four point bending mode increased from 217MPa for the monolithic counterpart to 387MPa. This was due to the optimal relationship where dispersoid size (L)≈dispersoid interval distance (S)≈process zone size (R p ). This was achieved locally within and around the porous Ti dispersoids, and helped improve the toughness and ductility. [Copyright &y& Elsevier]

The kinematic and isotropic hardening behavior was investigated for high and medium entropy alloys with a single-phase face-centered cubic (FCC) structure. The cross-slip associated with screw dislocations in FCC structures is strongly influenced by local fluctuations in the spatial distribution of different atom species. The local atomic arrangements inhibit the movement of Shockley partial dislocations during plastic deformation, thereby lowering the probability of cross-slip and generating a higher back-stress. This study used a solid-solution induced back-stress model, which combines nonlinear kinematic and isotropic hardening, to investigate the effects of dislocation forest stress and back-stress in a non-equiatomic Cr 12 Fe 42 Mn 24 Ni 22 medium entropy alloy. Based on the experimental results, numerical simulations by the finite element method were performed to validate this modeling approach. [ABSTRACT FROM AUTHOR]

[Display omitted] Recently-developed high-entropy alloys (HEAs) containing multiple principal metallic elements have extended the compositional space of solid solutions and the range of their mechanical properties. Here we show that the realm of possibilities can be further expanded through substituting the constituent metals with metalloids, which are desirable for tailoring strength/ductility because they have chemical interactions and atomic sizes distinctly different from the host metallic elements. Specifically, the metalloid substitution increases local lattice distortion and short-range chemical inhomogeneities to elevate strength, and in the meantime reduces the stacking fault energy to discourage dynamic recovery and encourage defect accumulation via partial-dislocation-mediated activities. These impart potent dislocation storage to improve the strain hardening capability, which is essential for sustaining large tensile elongation. As such, metalloid substitution into HEAs evades the normally expected strength-ductility trade-off, enabling an unusual synergy of high tensile strength and extraordinary ductility for these single-phase solid solutions. [ABSTRACT FROM AUTHOR]

• Nanoscale patterns were imprinted on FeCo-based metallic glass thin films. • A large mold fill factor was achieved for the imprinted patterns. • The thin-film magnetic properties were tailored by crystallization and the patterns. The ability to create submicron/nanoscale patterns with magnetic alloys at low cost is difficult. Here, we demonstrate a method to create such patterns using Fe 40 Co 35 P 10 C 10 B 5 metallic glass thin films. The viscous workability of a metallic glass thin film was used to make patterns with dimensions up to ~100 nm using the nanoimprinting technique, and the effects of the patterning on the magnetic properties of the metallic glass thin films were investigated. An increase in the out-of-plane coercivity (~380 Oe) and remanent magnetization (M r = ~12% of the saturation magnetization, M s) were observed for amorphous thin films patterned with a high density of nano-dots. This effect was observed because of changes to the magnetic shape anisotropy induced by the nano-imprinting. Two events of magnetization reversal were confirmed in the crystalline films of the same alloy. The reversal of magnetization under the low magnetic field of ~100 Oe corresponds to soft magnetic phases, whereas that at 2400 Oe corresponds to the hard magnetic phase. Recoil curve measurements suggest that the average magnetization-switching field of hard magnetic grains in the film was between 2800 and 3600 Oe. Based on our experimental results and analysis, we suspect the presence of tetragonal Fe–Co hard/semihard magnetic phase in crystalline thin films. We believe that the low-cost and large-area micro- to nanoscale patterning ability of the present magnetic thin films are promising for the development of various magnetic MEMS and memory devices. [ABSTRACT FROM AUTHOR]

A breakthrough in the strength and ductility trade-off is crucial for the development of advanced metallic materials. Herein, we present a novel heterostructured composite composed of immiscible magnesium (Mg) and ferrochrome (FeCr) with a 3D interconnected morphology and synthesized by liquid metal dealloying. Soft Mg and hard FeCr zones mutually interlock with each other. This unique interpenetrating-phase configuration leads to a significant alternation of their intrinsic mechanical properties, especially in the soft Mg zone. It causes a strong forest hardening effect, resulting in a high initial dislocation density, and the surrounding hard zones create hydrostatic pressure at the soft zone under tension. The measured yield strength of the composite is close to the upper rule of mixture while its tensile elongation is larger than that of the mixture. These outstanding mechanical properties originate from the synergetic interaction between the soft and hard zones through the immiscible interface zone. The current 3D interconnected heterogeneous composite acts a guideline for the design of advanced materials possessing physical properties beyond expectations. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel non-equiatomic FeCoNiAlTiMo ferrous medium-entropy alloy (MEA) with ultra-high tensile strengths at 298 and 77 K is presented in this work. By subjecting the MEA to hot rolling without further heat treatment, a quasi-dual-phase microstructure consisting of retained face-centered cubic (FCC) and thermal body-centered cubic martensite (BCC) phases with a very high density of dislocations and precipitates of Mo-rich µ phase was created. The high dislocation density significantly accelerated deformation-induced martensitic transformation from the remaining metastable FCC to BCC and successfully increased strain hardening ability. The strain hardening ability was even higher at 77 K due to decreasing FCC phase stability at lower temperatures. The increased strain hardening ability led to an excellent balance of strength and ductility, with ultimate tensile strength/uniform elongation of ~1.5 GPa/~15% at 298 K and ~2.3 GPa/~11% at 77 K. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel Fe-Ni-Co-Mn-Ti-Si MEA strengthened by heterogeneous microstructure was developed. • A superior combination of high-strength (YS ~ 930 MPa and UTS ~ 1075 MPa) and ductility (30%) has been achieved. • The deformation-induced martensitic transformation occurs during the straining of samples. • HDI and high plastic-incompatibility between the martensite and austenitic contributes to the high strength and ductility. In the work reported here, the mechanical properties of a newly developed Fe-Ni-Co-Mn-Ti-Si medium-entropy alloy with heterogeneous microstructure were investigated. High yield strength (~930 MPa), high ultimate tensile strength (~1100 MPa), and good ductility (~30%) were achieved using hetero-deformation-induced strengthening and high plastic-incompatibility between mechanically induced-martensite and the austenitic matrix. [ABSTRACT FROM AUTHOR]

Pure Ti shows promising performance for biomedical applications, but its strength needs to be greatly improved when used as heavy-load implants. In this work, β-Ti alloy was used as the reinforced layer to prepare Ti/β-Ti alloy laminated composite through Spark Plasma Sintering (SPS) with hot/cold rolling and partial recrystallization annealing. The microstructural evolution of Ti layer, β-Ti alloy layer and the interface between them during the fabrication process was investigated. The results showed the composite comprises alternating recrystallized Ti layer, β-Ti alloy layer with deformed microstructure, and α+β dual phase interface layer containing submicron sized rod-like or granular α phase. Besides, the deformation behavior and mechanical properties of the Ti/β-Ti alloy laminate composite were studied. The Ti/β-Ti alloy laminate composite after partial recrystallization annealing shows a good match of high strength and good ductility (tensile strength: 832 MPa and uniform elongation: 20%), owing to the co-work of the diffusion interface layer and the constraint effect. The α+β dual phase layer has an important effect on weakening the deformation incompatibility between Ti layer and β-Ti alloy layer and preventing crack propagation during the tensile deformation. [ABSTRACT FROM AUTHOR]

Medium-entropy alloys strengthened by the L1 2 -type coherent precipitates were recently proposed, whereas the mechanical property still needs to be improved. Here, we demonstrated a strategy for notably improving the strength of the representative (CoCrNi) 94 Ti 3 Al 3 alloy, in which the refinement of grain structures and the promotion of precipitation were concurrently achieved by pre-strain followed by aging. A refined grain structure containing incoherent σ-precipitates and a large number of coherent L1 2 -precipitates was formed, which enhances the yield strength and ultimate tensile strength up to 1431 MPa and 1683 MPa respectively. Furthermore, decreasing pre-strain temperature or increasing strain further aids the enhancement. The present study opens an avenue for fabricating high-performance precipitation-strengthened alloys. [ABSTRACT FROM AUTHOR]

In this study, quasi-static tensile properties of Fe 60 Co 15 Ni 15 Cr 10 (at%) ferrous medium-entropy alloy at 298 K and 77 K were investigated in terms of thermally-activated deformation mechanism. Relatively high strain rate sensitivity and low activation volume were estimated using strain rate jump tests at 77 K where deformation-induced martensitic transformation took place, compared to those at 298 K. Different rate-controlling mechanisms were identified for early and latter deformation at both temperatures considering the plastic strain. Dislocation behaviors, e.g., cross-slip or dislocation accumulation, based on the thermally-activated deformation mechanism, support the outstanding cryogenic tensile properties of the present alloy. • Thermally activated behaviors of a ferrous medium-entropy alloy were investigated. • High strain rate sensitivity and low activation volume were obtained at 77 K. • The unique rate-controlling mechanisms were identified upon temperature and strain. • Inhibited cross-slip supports superior cryogenic tensile properties of the alloy. [ABSTRACT FROM AUTHOR]

Low modulus biomaterials are in focus as potential candidates for biomedical implants ensuring a fast healing of hard tissues. The close match between elastic properties of an implant material and bone are critical to eliminate stress-shielding effect. In this study, we synthesized a low modulus interpenetrating-phase composite of Ti and Mg by liquid metal dealloying. Its Young's modulus value is in the range of that found for human bone which allows for biomedical applications of this material. Unexpectedly, the Young's modulus value of the composite (17.6 GPa) is several times lower than that of each individual constituent phases, namely, Mg (45 GPa) and Ti (110 GPa). Using micromechanical modelling, it is demonstrated that the origin of the anomalously low modulus can be related to a weakened interface between the constituents. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Glass-forming ability of metallic glasses is investigated by hyper-ordered structures. • Intermediate-range structures of Pd 40 Cu 40 P 20 are compared with those of Pd 40 Ni 40 P 20. • Important features are found in Voronoi tessellation and persistent homology analyses. To clarify the relationship between the glass- forming ability (GFA) and local atomic structure of Pd-based metallic glasses, the structures of an amorphous Pd 40 Ni 40 P 20 are investigated by anomalous X-ray scattering and neutron diffraction with help of reverse Monte Carlo modeling, and important structural features characteristic to the GFA are found in the hyper-ordered structures, such as persistent homology ring sizes, in comparison with those of Pd 40 Ni 40 P 20 glass. To clarify the relationship between the glass-forming ability (GFA) and local atomic structure of Pd-based metallic glasses, the structures of an amorphous Pd 40 Cu 40 P 20 (PCP) were investigated using the same methods as for Pd 40 Ni 40 P 20 (PNP) metallic glass, i.e., by a combination of anomalous X-ray scattering, X-ray and neutron diffraction, and reverse Monte Carlo modeling. From the comparison between the results of PNP with an excellent GFA and the PCP with a worse GFA, important features characteristic to the GFA are found in the hyper-ordered structures. Firstly, the compositional inhomogeneity of Cu in PCP is larger than Ni in PNP. Secondly, a Voronoi tessellation reveals that icosahedral arrangements are found with considerable probability around the Ni atoms in PNP, while a less existence around the Cu atoms in PCP. Thirdly, a persistent homology (PH) analysis shows smaller intermediate-size Cu PH rings in PCP than Ni PH rings in PNP. [ABSTRACT FROM AUTHOR]

• Substituting few percents of Cu in TiZrCuPd BMG improves its passive behavior. • Sn and Si elements play a beneficial role on the metallurgical quality of BMG. • Heterogeneity within solid solution and casting defects act as weakening sites. • Adding Sn and Si elements limit the susceptibility to pitting corrosion. In this work, the effect of substituting Cu with small amounts of Sn and Si on the passive behavior and pitting resistance of the bulk metallic glass Ti 40 Zr 10 Cu 36 Pd 14 was investigated. The Sn/Si substitution promoted homogenization of the solid solution and limited the presence of casting defects. In addition, unlike the heterogeneous passive film grown on TiZrCuPd, the passive films of the micro-alloyed materials were homogeneous, implying less sensitivity to film weakening and breakdown. Thus, alloying with small amounts of Sn and Si appears to be a viable approach to drastically improve the corrosion resistance of TiZrCuPd. [ABSTRACT FROM AUTHOR]

• Microporous ferritic stainless steel was produced from Incoloy 800 via LMD. • LMD can be used industrially to produce inexpensive porous materials. • Minor elements in commercial alloys tend to slow down coarsening kinetics. • Nitric acid that serves for Mg dissolution also induces a passivation treatment. • The pore size (0.5–1.5 μm) has no significant effect on pitting sensitivity. • The pore size plays a role on diffusion processes through the porous structure. Liquid metal dealloying is a newly available technology used to create bulk porous materials. In this study, a commercial nickel-based superalloy, Incoloy 800, was dealloyed to elaborate a fully porous ferritic stainless steel. The Mg selective dissolution in nitric acid solution acts as a passivation treatment that enhances the passive film resistance. Corrosion tests confirm the beneficial effect of the nitric acid treatment on the Cr enrichment of the passive film thus improved the material resistance. The electrochemical characterizations show a higher effect of the size porosities on the diffusion kinetics of the electrolyte rather than on the pitting sensitivity. [ABSTRACT FROM AUTHOR]

We investigated the nanoscale anisotropic deformation behavior of Al-supersaturated α 2 -Ti 3 Al single crystals, using wedge indentation with the loading axis parallel to the (0001) α 2 basal plane. The deformability, plastic deformation mechanism, and introduced dislocation structures beneath the indentations were notably affected by the inclination angle between the indenter edge and basal plane. Notably, abnormal dislocation bands were introduced when the edge was parallel to the (0001) plane, which can potentially be utilized for manipulating the phase decomposition locally. The present study sheds light on the regulation of local plastic deformation and manipulation of nanoscale phase transformation in metals and alloys. Image 1 • The local deformation behavior of Al-supersaturated α 2 -Ti 3 Al single crystals was firstly investigated by wedge indentation. • The deformation behavior is notably affected by the orientation relationship between indenter and basal plane of crystal. • Regulated periodic basal dislocations for manipulating phase decompositions is successfully introduced. [ABSTRACT FROM AUTHOR]

Crack-free nanocellular graphenes are attractive materials with extraordinary mechanical and electrochemical properties, but their homogeneous synthesis on the centimeter scale is challenging. Here, a strong nanocellular graphene film achieved by the self-organization of carbon atoms using liquid metal dealloying and employing a defect-free amorphous precursor is reported. This study demonstrates that a Bi melt strongly catalyzes the self-structuring of graphene layers at low processing temperatures. The robust nanoarchitectured graphene displays a high-genus seamless framework and exhibits remarkable tensile strength (34.8 MPa) and high electrical conductivity (1.6 × 10 4 S m -1 ). This unique material has excellent potential for flexible and high-rate sodium-ion battery applications., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Metastability engineering is a strategy to enhance the strength and ductility of alloys via deliberately lowering phase stability and prompting deformation-induced martensitic transformation. The advantages of the strategy are widely exploited by ferrous medium-entropy alloys (MEAs) that exhibit phase transformation from metastable face-centered cubic (FCC) to hexagonal close-packed (HCP) or body-centered cubic (BCC) martensite and a significant increase in work hardening. Fe 50 Co 25 Ni 10 Al 5 Ti 5 Mo 5 (at%) MEA is an example of such materials, which shows ~1.5 GPa of tensile strength assisted by exceptional work hardening from the deformation-induced BCC martensitic transformation. In this work, the martensitic transformation and its effect on the mechanical response of the MEA were studied by in situ neutron diffraction under tensile loading. Strain-induced BCC martensite started forming rapidly from the beginning of plastic deformation, reaching a phase fraction of ~100% when deformed to ~10% of true strain. Lattice strain and phase stress evolution indicate that stress was dynamically partitioned onto the newly formed BCC martensite, which is responsible for the work hardening response and high flow stress of the MEA. This work shows how great a role FCC to BCC martensitic transformation can play in enhancing the mechanical properties of ferrous MEAs., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2022 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis Group.)

Intermetallic compounds formed from non-precious transition metals are promising cost-effective and robust catalysts for electrochemical hydrogen production. However, the development of monolithic nanoporous intermetallics, with ample active sites and sufficient electrocatalytic activity, remains a challenge. Here we report the fabrication of nanoporous Co 7 Mo 6 and Fe 7 Mo 6 intermetallic compounds via liquid metal dealloying. Along with the development of three-dimensional bicontinuous open porosity, high-temperature dealloying overcomes the kinetic energy barrier, enabling the direct formation of chemically ordered intermetallic phases. Unprecedented small characteristic lengths are observed for the nanoporous intermetallic compounds, resulting from an intermetallic effect whereby the chemical ordering during nanopore formation lowers surface diffusivity and significantly suppresses the thermal coarsening of dealloyed nanostructure. The resulting ultrafine nanoporous Co 7 Mo 6 exhibits high catalytic activity and durability in electrochemical hydrogen evolution reactions. This study sheds light on the previously unexplored intermetallic effect in dealloying and facilitates the development of advanced intermetallic catalysts for energy applications., (© 2022. The Author(s).)

Surface plasmon resonance is a well-established technology for real-time highly sensitive label-free detection and measurement of binding kinetics between biological samples. A common drawback, however, of surface plasmon resonance detection is the necessity for far field angular resolved measurement of specular reflection, which increases the size as well as requiring precise calibration of the optical apparatus. Here we present an alternative optoelectronic approach in which the plasmonic sensor is integrated within a photovoltaic cell. Incident light generates an electronic signal that is sensitive to the refractive index of a solution via interaction with the plasmon. The photogenerated current is enhanced due to the coupling of the plasmon mode with Fabry-Pérot modes in the absorbing layer of the photovoltaic cell. The near field electrical detection of surface plasmon resonance we demonstrate will enable a next generation of cheap, compact and high throughput biosensors., (© 2021. The Author(s).)

Glass transition is one of the unresolved critical issues in solid-state physics and materials science, during which a viscous liquid is frozen into a solid or structurally arrested state. On account of the uniform arrested mechanism, the calorimetric glass transition temperature (T g ) always follows the same trend as the dynamical glass transition (or α-relaxation) temperature (T α ) determined by dynamic mechanical analysis (DMA). Here, we explored the correlations between the calorimetric and dynamical glass transitions of three prototypical high-entropy metallic glasses (HEMGs) systems. We found that the HEMGs present a depressed dynamical glass transition phenomenon, i.e., HEMGs with moderate calorimetric T g represent the highest T α and the maximum activation energy of α-relaxation. These decoupled glass transitions from thermal and mechanical measurements reveal the effect of high configurational entropy on the structure and dynamics of supercooled liquids and metallic glasses, which are associated with sluggish diffusion and decreased dynamic and spatial heterogeneities from high mixing entropy. The results have important implications in understanding the entropy effect on the structure and properties of metallic glasses for designing new materials with plenteous physical and mechanical performances.

Titanium carbide (TiC), is the most thermodynamically stable compound in the Ti-C-Cu system, which makes it a suitable reinforcement phase for copper matrix composites. In this work, the interaction of a Ti-Cu alloy with different forms of carbon was investigated to trace the structural evolution leading to the formation of in-situ TiC-Cu composite structures. The reaction mixtures were prepared from Ti 25 Cu 75 alloy ribbons and carbon black or nanodiamonds to test the possibilities of obtaining fine particles of TiC using ball milling and Spark Plasma Sintering (SPS). It was found that the behavior of the reaction mixtures during ball milling depends on the nature of the carbon source. Model experiments were conducted to observe the outcomes of the diffusion processes at the alloy/carbon interface. It was found that titanium atoms diffuse to the alloy/graphite interface and react with carbon forming a titanium carbide layer, but carbon does not diffuse into the alloy. The diffusion experiments as well as the synthesis by ball milling and SPS indicated that the distribution of TiC particles in the composite structures obtained via reactive solid-state processing of Ti 25 Cu 75 +C follows the distribution of carbon particles in the reaction mixtures. This justifies the use of carbon sources that have fine particles to prepare the reaction mixtures as well as efficient dispersion of the carbon component in the alloy-carbon mixture when the goal is to synthesize fine particles of TiC in the copper matrix., Competing Interests: The authors declare no conflict of interest.