A novel immiscible high entropy alloy strengthened via L1₂-nanoprecipitate

The low-cost Fe-Cu, Fe-Ni, and Cu-based high-entropy alloys exhibit a widespread utilization prospect. However, these potential applications have been limited by their low strength. In this study, a novel Fe₃₁Cu₃₁Ni₂₈Al₄Ti₃Co₃ immiscible high-entropy alloy (HEA) was developed. After vacuum arc melting and copper mold suction casting, this HEA exhibits a unique phase separation microstructure, which consists of striped Cu-rich regions and Fe-rich region. Further magnification of the striped Cu-rich region reveals that it is composed of a Cu-rich dot-like phase and a Fe-rich region. The aging alloy is further strengthened by a L1₂-Ni₃(AlTi) nanoprecipitates, achieving excellent yield strength (1185 MPa) and uniform ductility (∼8.8%). The differential distribution of the L1₂ nanoprecipitate in the striped Cu-rich region and the external Fe-rich region increased the strength difference between these two regions, which increased the strain gradient and thus improved hetero-deformation induced (HDI) hardening. This work provides a new route to improve the HDI hardening of Fe-Cu alloys.