Excelling mechanical response of a powder metallurgy medium entropy alloy under extreme loading conditions

Elevated temperatures coupled with dynamic loads present formidable challenges in advanced applications. Using advanced powder metallurgy (PM), CoCrNi, an FCC alloy, was crafted with ultrafine-grained microstructure devoid of any second phase, oxides, or precipitates. Despite the ultrafine microstructure, the material retains its work hardening at room and elevated temperatures. The yield strength of PM alloy shows a 300 % elevation compared to cast alloy at room temperature. Microstructural analysis revealed that mechanical performance stems from the synergistic effect of refined microstructure and nano-domain defects, including stacking faults, dislocations, twining, and nano-grains in raw materials. During dynamic deformation, multivariant twins evolved to contribute towards strengthening and work hardening. Saliently, the alloy exhibits remarkable high-temperature strength and resilience without softening or fracturing. The presence of nano-twins at high temperatures is one of the reasons for the thermal stability of material at elevated temperatures.