Effect of annealing treatments on microstructure, tensile and wear properties of cold-rolled FeCoCrNiMn high entropy alloy

Abstract

The equiatomic FeCoCrNiMn is a highly studied high-entropy alloy (HEA) known for its exceptional properties. In this study, FeCoCrNiMn HEAs with varying grain sizes were prepared by heavy cold rolling and subsequent annealing at 900 °C for different durations. Ultrafine-grained sample with an average grain size of about 0.75 μm was obtained after annealing for 2 min, which displayed an enhanced strength-ductility combination with a yield strength of around 620 MPa, an ultimate strength of around 778 and a tensile elongation of over 30 %. Grain boundary strengthening contributed significantly to the mechanical strength of the resulting alloy. The grain size of the alloy increased with annealing times, aligning well with the linear Hall-Petch relationship, and the processed HEA demonstrated the expected strength-ductility trade-off. The ultrafine-grained sample exhibited improved wear performance with reduced wear rate and improved worn surface characteristics compared to the coarser-grained samples. The wear mechanism of the FeCoCrNiMn alloy primarily involved abrasive wear and oxidative wear.