Effect of heterogeneous microstructure on the mechanical and corrosion properties of FeCoCrNiMn-(N, Si) high entropy alloy

Designing high entropy alloys (HEAs) with both high mechanical properties and good corrosion performance is essential. In this study, FeCoCrNiMn-(N, Si) HEAs with harmonic structure (HS) and partially recrystallized structure were prepared by powder metallurgy and thermomechanical processing, respectively. Their microstructure, mechanical properties, and corrosion behavior were systematically investigated. The HS sample has a microstructure where coarse grains are surrounded by fine grains. Nanotwins, microbands, and planar dislocations were the main deformed microstructure in FeCoCrNiMn-(N, Si) HEAs, contributing to a steady strain hardening rate. The partially recrystallized structure can effectively enhance mechanical properties but deteriorate the corrosion properties. In addition, the HS sample, which was fabricated by mixing coarse and fine powders, exhibited better strength and corrosion properties in comparison with the sample with a homogenized structure prepared using fine powders. Hence, this study demonstrates a method that allows the use of large size powders to achieve satisfactory properties while minimizing material waste.