Effect of aging temperature on microstructure and mechanical properties of Fe–Ni–Cr–Al high entropy alloy

Abstract

Investigating the strength–plasticity synergy of metal structural materials is a crucial scientific challenge. This study focuses on preparing high-entropy alloys (HEAs) comprising Fe–Ni–Cr–Al, which exhibit a heterostructural coexistence of several phases through cold rolling and aging (CRA). Above 600 °C CRA, the average grain size of the HEA was refined from 260 to 1.64 μm, and numerous annealing twins were formed. Concurrently, two forms of irregularly ordered body-centred cubic (B2) phases and nanoscale ordered face-centred cubic (L12) phases were precipitated. Large B2 particles precipitated along the grain boundary, whereas small B2 and L12 particles precipitated within the grains. The average sizes of the B2 and L12 particles were 510 and 2.21 nm, respectively. The fine grain and precipitation strengthening enhanced the HEA yield strength (from 254 to 710 MPa). The difference in plastic strain between the matrix and precipitate causes long-range back-stress strengthening and heterodeformation-induced hardening, enhancing the strain-hardening ability and maintaining the superior plasticity of the HEA. This study provides an effective approach for obtaining metal structural materials with strength–plasticity synergy.