Effect of Microstructure on the Deformation Mechanism of Friction Stir-Processed Al0.1CoCrFeNi High Entropy Alloy

Grain refinement from several millimeters in as-received (AR) condition to the range of 0.35–15 μm was achieved by friction stir processing (FSP). Due to the sluggish nature of atomic diffusion in high entropy alloys (HEAs), the FSP region exhibited an immense variation in microstructure which was directly attributed to the accumulated plastic strain during FSP. In accordance with the Hall–Petch relationship, yield strength (YS) has increased by a factor of four after grain refinement while maintaining large uniform elongation (UE). The Kocks–Mecking plot indicated different deformation mechanisms operative in both FSP and AR conditions.