Metallurgy

Commercial maraging alloys provide high strength and toughness by traditional precipitation strengthening mechanism. Here, the authors demonstrate a new strategy involving deformable precipitates and their dynamic phase transformation resulting in a twofold enhancement of strength and ductility.

Unlike diffusion-mediated chemical short-range orders (SROs) in multi-principal element alloys, diffusionless SROs and their impact on alloys have been elusive. Here, the authors show the formation of strain-induced SROs by crystalline lattice defects, upon external loading at 77 K.

Dislocations in high-entropy alloys encounter pinning during glide resulting in jerky motion. Here the authors demonstrate that the density of high local Peierls force is proportional to the critical stress required for their glide and mobility.

The ever most widely used eutectic alloys often suffer from limited ductility. Here the authors propose a distinctive concept of phase-selective recrystallization to significantly improve their ductility and strength and pave the way for new applications of the widespread eutectic alloys.

Mechanical twinning is difficult to trigger in face centered cubic alloys with high stacking fault energies (SFEs) under standard tensile loading. Here, the authors report high stress twinning in a bulk compositionally complex steel of very high SFE, enhancing the material’s mechanical performance.

Compositional heterogeneity in high-entropy alloys (HEAs) has gained lots of attention, but its relation with the properties remains vague. Here the authors report an anomalous size effect on strength by the compositional heterogeneity, which provides new insights in its connection to properties.

Interstitials can substantially strengthen metals. Here the authors show a massive interstitial solid solution (MISS) approach enabling a model multicomponent alloy to achieve near-theoretical strength together with large deformability.

The existence of chemical medium-range order (CMRO) in high- and medium- entropy alloys remains conjectural. Here the authors show evidences of CMRO by electron diffraction spots of lattice periodicity, observable entities, occupancy of preferential species, and stable sizes upon deformation.

The strength in BCC high-entropy alloys is associated with the type of mobile dislocations. Here the authors demonstrate by means of an ample array of experimental techniques that edge dislocations can control the strength of BCC high-entropy alloys.

The strength-ductility trade-off has been a long-standing problem for alloy development. Here the authors present a route for designing high-entropy alloys to overcome this trade-off via short-range ordering shown by combined Monte Carlo, molecular dynamic, and density-functional theory simulations.

Precipitation hardening, used as an effective strengthening strategy in various alloy systems, has been usually achieved by coherent precipitates. Here, the authors develop ultrastrong ductile alloys employing structurally dissimilar semicoherent precipitates by shear band-driven precipitation.

A fundamental understanding of fatigue-failure mechanisms is key to develop robust structural materials. Here the authors report a high entropy alloy with enhanced fatigue life by ductile transformable multicomponent B2 precipitates, as revealed by combined experimental and simulation methods.

Strong and ductile materials with resistance to both corrosion and hydrogen embrittlement remain rare and yet are essential for hydrogen-propelled industries. Here, the authors show that a CoNiV medium-entropy alloy with face-centered cubic structure fulfils all the above criteria.

Superplasticity at high strain rates is challenging to achieve in high strength materials. Here, the authors show superplastic elongation in excess of 2000% in a high entropy alloy nanostructured by high-pressure torsion.

Chemical short-range order (SRO) NiCoCr has been proposed to account for its positive stacking fault energy and good mechanical properties. Here, a combination of theory and experiment shows that SRO is of negligible importance in NiCoCr processed by standard methods.

Improving both strength and ductility simultaneously in structural metals and alloys remains a challenge. Here, the authors design a heterogeneous structure in a Co-Cr-Ni alloy that results in ultrahigh strength and significant uniform elongation.

In dual-phase Cantor-like high entropy alloys, how local chemistry affects enhanced deformation mechanisms remains unclear. Here, the authors image 3D stacking fault networks formation and show they both impede dislocations and facilitate phase transformations via local chemical composition variations.

Multi-principal-element alloys have been assumed to have the configurational entropy of an ideal solution. Here, the authors use atomistic simulations to show that instead NiCoCr exhibits local chemical order, raising the activation barriers of dislocation activities to elevate mechanical strength.

The identification of high entropy alloys is challenging given the vastness of the compositional space associated with these systems. Here the authors propose a supervised learning strategy for the efficient screening of high entropy alloys, whose hardness predictions are validated by experiments.

Designing complex concentrated alloys with targeted properties for high performance remains challenging because of their complex local atomic environments. Here, the authors show how to engineer atomic-level pressure to customize complexity-induced properties such as solid-solution strengthening.

Additive manufacturing of high entropy alloys is still an emerging field that usually relies on expensive pre-alloyed powders. Here, the authors develop a method to 3D ink-print a CoCrFeNi high entropy alloy using inexpensive blended oxide nanopowders, hydrogen reduction, and sintering.

Medium entropy alloy CoCrNi has better mechanical properties than high entropy alloys such as CrMnFeCoNi, but why that is remains unclear. Here, the authors show that a nanostructured phase at lattice defects in CoCrNi causes its extraordinary properties, while it is magnetically frustrated and suppressed in CrMnFeCoNi.