Effect of cold-working on phase formation during heat treatment in CrMnFeCoNi system high-entropy alloys with Al addition

An equiatomic CrMnFeCoNi alloy is usually a single-phase solid-solution with a face-centered cubic (fcc) structure. However, a Cr-rich sigma phase with a tetragonal structure is formed in coarse-grained alloys after extended heat treatment between 873 K and 1073 K, which is indicative of metastability of the CrMnFeCoNi alloy. In this study, it was demonstrated that cold-working facilitated sigma-phase formation during heat treatment at 1073 K in (CrMnFeCoNi)(100-x)Al-x (x = 8 and 9 at%). More specifically, the heat treatment produced a unique sigma-body-centered cubic (bcc) aggregate morphology in the unrecrystallized fcc matrix. Each aggregate was composed of sigma-phase spine and bcc particles at the fcc/sigma interface, and formed in a short period (0.5 h). It is suggested that aggregates precipitated on dislocations that were introduced by cold-working. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Cold-working was found to facilitate the formation of sigma phase in CrMnFeCoNi alloy under specific heat treatment conditions. The resulting sigma-body-centered cubic (BCC) aggregates consist of sigma phase spines and BCC particles, forming rapidly at the face-centered cubic/sigma interface.