Refinement strengthening, second phase strengthening and spinodal microstructure-induced strength-ductility trade-off in a high-entropy alloy

The strength-ductility trade-off of high-entropy alloy (HEA) is a major factor affecting its potential application. In this work, the mechanical properties and deformation mechanisms of as-cast and cold rolled-annealed (RA) Fe23Co24Ni24Cr21Al8 (at%) HEA samples were comparatively investigated. Compared with as-cast sample, the cold-rolled and annealed sample possessed higher yield strength (725 +/- 12 MPa), ultimate strength (1042 +/- 23 MPa) and sustained good ductility (46.7 +/- 4.5%), suggesting excellent strength-ductility combination was achieved in RA sample. The as-cast and RA samples both possessed dual phases including FCC and BCC, but the volume fraction of BCC in as-cast sample was very few. The RA sample exhibited significantly decreased grain size and more volume fraction of BCC compared with as-cast sample, indicative of the refinement strengthening and second phase strengthening. Meanwhile, a high density of dislocation walls and spinodal decomposition structure were observed in RA sample, which contributed to the outstanding ductility.

Automated summary

This study investigated the mechanical properties and deformation mechanisms of as-cast and cold rolled-annealed high-entropy alloy samples. The cold-rolled and annealed sample showed higher yield strength, ultimate strength, and good ductility compared to the as-cast sample. The RA sample exhibited significant changes in grain size, phase volume fraction, and dislocation walls.