Here we report on the tensile deformation behavior of a face-centered cubic (FCC)-structured Fe₄₅Co₂₅Ni₁₀V₂₀ high-entropy alloy at cryogenic temperature (77 K). The alloy displays an impressive 1.1 GPa tensile strength while maintaining an ultrahigh fracture elongation of 82% with a minimum strain hardening rate at a true strain of about 40%. We elucidate such unique mechanical properties, originating from the strain-induced FCC to body-centered cubic (BCC) martensitic transformation, where the high-stress concentrations at grain boundaries or intersection of stacking faults can stimulate phase transition. The martensitic transformation can induce strain softening by consuming the stored deformation energy while contributing to the strain hardening via the transformation itself and further deformation of BCC phases. Such a dynamic balance between softening and hardening enables a relatively uniform plastic flow, resulting in a plastic deformation with a strain range of up to 35% delaying macroscopic necking. The findings provide further insights into the significance of transformation-induced plasticity effects on the cryogenic performance of alloys.

在这里，我们报告了面心立方 (FCC) 结构的 Fe ₄₅ Co ₂₅ Ni ₁₀ V _{20的拉伸变形行为}低温 (77 K) 下的高熵合金。该合金显示出令人印象深刻的 1.1 GPa 抗拉强度，同时保持 82% 的超高断裂伸长率以及在约 40% 的真实应变下的最小应变硬化率。我们阐明了这种独特的机械性能，起源于应变诱导的 FCC 到体心立方 (BCC) 马氏体转变，其中晶界或堆垛层错相交处的高应力集中可以刺激相变。马氏体相变可以通过消耗存储的变形能引起应变软化，同时通过相变本身和 BCC 相的进一步变形促进应变硬化。这种软化和硬化之间的动态平衡使塑性流动相对均匀，导致塑性变形，应变范围高达 35%，从而延迟宏观颈缩。这些发现进一步深入了解了相变诱导的塑性效应对合金低温性能的重要性。