# Improving Mechanical Properties of Fe-Mn-Co-Cr High-Entropy Alloy via Annealing after Cold Rolling

## TL;DR

This study shows that annealing a high-entropy alloy at 1000°C after cold rolling improves its strength and plasticity by promoting grain growth and twin formation.

## Contribution

The novel finding is that 1000°C annealing enhances mechanical properties through complete recrystallization and TWIP mechanism activation.

## Key findings

- Annealing at 1000°C leads to higher tensile strength (~885 MPa) and elongation (~68%) compared to lower temperatures.
- Higher volume of annealing twins at 1000°C enhances plasticity via the TWIP mechanism.
- Annealing at 900°C and 950°C results in uneven grain size and σ phase precipitation at grain boundaries.

## Abstract

The as-cast (Fe50Mn30Co10Cr10)97C2Mo1 HEA (high entropy alloy) was prepared and cold-rolled at 70%. Subsequently, annealing heat treatment at different temperatures (900 °C, 950 °C, 1000 °C) was carried out. The microstructure evolution and mechanical properties of the HEA were systematically investigated. The results showed that the HEA annealed at 900 °C and 950 °C exhibited uneven grain size and rich σ precipitation phase at grain boundaries. The grains began to grow and complete recrystallization, and no σ phases were observed in HEA annealed at 1000 °C, which resulted in a higher tensile strength of ~885 MPa and elongation of ~68% compared with other annealed HEAs. The higher volume fraction of annealing twins with 60°<111> orientation was produced in HEA annealed at 1000 °C, which enhanced the tensile strength and plasticity via the Twinning-induced plasticity (TWIP) mechanism.