Owing to superior strength-ductility combination and great potential for applications in extreme conditions, high-entropy alloys (HEAs) with the face-centered cubic (FCC) structure have drawn enormous attention. However, the FCC structure limits yield strength and makes the alloys unable to meet ever-increasing demands for exploring the universe. Here, we report a strategy to obtain FCC materials with outstanding mechanical properties in both ambient and cryogenic environments, via exploiting dynamic development of the interstitial-driven local chemical order (LCO). Dense laths composed of the multiscaled LCO domains evolve from planar-slip bands that form in the prior thermomechanical processing, contributing to ultrahigh yield strengths over a wide temperature range. During cryogenic tensile deformation, LCO further develops and promotes remarkable dislocation cross-slip. Together with the deformation-driven transformation and twinning, these factors lead to satisfactory work hardening. The cryogenic loading–promoted LCO, also revealed by ab initio calculations, opens an avenue for designing advanced cryogenic materials.

Deformation incompatibility in Ti/Nb laminates under uniaxial tension was revealed by in-situ neutron diffraction. During uniform deformation of the bulk laminates, the hard Nb constrained by the soft Ti showed moderate work hardening and only slightly decreased flow stress. The mechanical incompatibility accumulated in both elastic and elasto-plastic regimes between the metals lead to pronounced hetero-deformation induced (HDI) strengthening, and the HDI stress was comparable to the maximum phase-to-phase interaction. The HDI hardening and interphase stress showed consistent evolution trends, implying that the interaction between dissimilar metals can be used as an important indicator for evaluating HDI strengthening and hardening. GRAPHICAL ABSTRACT The phase-to-phase interaction is found to be an important indicator for evaluating the HDI strengthening and hardening in heterogeneous laminates, and the microstress analysis can guide the design of heterostructures.

Ultrahigh strength and good ductility are obtained for two low-alloy transformation-induced-plasticity steels fabricated by the quenching and partitioning (Q&P) processing, respectively. Compared to 0.19 wt.% C steel in which γ → α′-martensite transformation is the dominant mechanism under deformation, the relatively high C content of austenite in 0.47 wt.% C steel is responsible for the transformation from γ to ε-martensite, suggesting that the transformation is not solely determined by the stacking fault energy. The study shows that during the Q&P process, strong and ductile steels with specific transformation procedures can be obtained by adjusting volume fraction and carbon content of the retained austenite.

Valence electron concentration (VEC) is a crucial parameter affecting the structure and mechanical properties of materials. Nevertheless, the influence of VEC in multicomponent alloys remains muddy. Here, the correlations between VEC and phase stability, intrinsic mechanical strength, and deformation mechanism are revealed by investigating six equiatomic $\mathrm{CoNi}M$ ($M$ = Ti, V, Cr, Mn, Fe, and Cu) alloys with VEC ranging from 7.7 to 10.0. As VEC increases, the ground-state structure evolves from bcc to hcp and ultimately to fcc. Both elastic moduli and ideal tensile strength increase initially and then decrease with increasing VEC, i.e., an inverted parabolic trend, which arises due to the orbital-filling effect of valence electrons. We highlight that a medium VEC ($\sim 8.3$) has superior intrinsic strength at a full filling of the bonding state but an empty antibonding state. Furthermore, a strong link between intrinsic strength and the energy difference between bcc and fcc ($\mathrm{\Delta }{E}_{\mathrm{fcc}\to \mathrm{bcc}}$) is built. The stacking fault (SF) energy ${\gamma }_{\mathrm{sf}}$ roughly increases with VEC except for in CoNiCr; this correlation is inherited from the energy difference between fcc and hcp. The dependence of intrinsic deformation energy barriers on VEC follows that of $\mathrm{\Delta }{E}_{\mathrm{fcc}\to \mathrm{bcc}}$ since both are linked to the bonding strength. Depending on orientation, dislocation slip (SL) and SF can co-occur in the alloys with low VEC while SL and twinning (TW) coexist in those with high VEC. Both competition between SF or TW and SL and competition between SF and TW are dictated by ${\gamma }_{\mathrm{sf}}$. This work unveils relations between VEC and phase stability, intrinsic strength, and deformation mechanisms and could provide some useful information for designing novel multicomponent alloys.