Achieving superior combined cryogenic strength and ductility in a high-entropy alloy via the synergy of low stacking fault energy and multiscale heterostructure

A Co30Cr20Fe18Mn18Ni11Si3 high-entropy alloy (HEA) with low stacking fault energy and high strengthen was designed based on the principle of heterostructure strengthening. The alloy was processed into a multiscale heterogeneous microstructure containing hierarchical twins. The alloy achieved an ultrahigh yield strength of 1500 MPa, ultimate tensile strength of 1750 MPa and a large ductility of 20 % at 77 K. These mechanical properties were superior to those of most FCC HEAs reported in the literature, breaking the strength-ductility trade-off of conventional metal alloys. Such extraordinary mechanical properties were attributed to a suitable strain hardening capability, stemming from the synergistic effect of hetero-deformation-induced hardening, twinning-induced plasticity, and deformation-induced phase transformation during tensile deformation.

Automated summary

A high-entropy alloy (HEA) with low stacking fault energy and high strength was designed using the principle of heterostructure strengthening. The alloy exhibited a multi-scale heterogeneous microstructure containing hierarchical twins. It achieved ultrahigh yield strength, ultimate tensile strength, and large ductility at low temperature, surpassing most FCC HEAs reported so far and breaking the strength-ductility trade-off of conventional metal alloys. The extraordinary mechanical properties were attributed to a suitable strain hardening capability resulting from the synergistic effect of hetero-deformation-induced hardening, twinning-induced plasticity, and deformation-induced phase transformation.