Exceptional Phase-Transformation Strengthening of Fe50Mn20Cr20Ni10 Medium-Entropy Alloys at Cryogenic Temperature

Cobalt-free Fe50Mn20Cr20Ni10 medium-entropy alloys were developed with the metastable engineering strategy at cryogenic temperature. The phase formation rules were calculated and the stacking fault energy was estimated at different temperatures. The uniaxial tensile tests were carried out at a cryogenic temperature and the mechanical properties were completely investigated, displaying excellent strain-hardening capacity. The deformation mechanisms were systematically explained by forest dislocation, twinning strengthening, and phase-transformation strengthening at cryogenic temperature. The precipitation of the second phase sacrifices some ductility, but still achieves excellent strong-plastic synergy.