Unraveling the deformation behavior of the Fe45Co25Ni10V20 high entropy alloy

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 inter-section 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.

Automated summary

In this study, the tensile deformation behavior of a face-centered cubic (FCC)-structured Fe45Co25Ni10V20 high-entropy alloy at cryogenic temperature (77 K) is investigated. The alloy exhibits an impressive tensile strength of 1.1 GPa and an ultrahigh fracture elongation of 82%, with minimum strain hardening rate at a true strain of about 40%. These unique mechanical properties are attributed to the strain-induced FCC to body-centered cubic (BCC) martensitic transformation, which is stimulated by high-stress concentrations at grain boundaries or inter-section of stacking faults. The martensitic transformation induces strain softening by consuming stored deformation energy and contributes to strain hardening through the transformation itself and further deformation of BCC phases. This dynamic balance between softening and hardening enables a relatively uniform plastic flow, resulting in 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.