Microstructure and micromechanical responses of bulk nanostructured high entropy alloy after heavy-ion irradiation at 500C

Nanocrystalline materials possess high defect-sink density, but often experience radiation-enhanced grain coarsening. With the intrinsic sluggish diffusion and radiation tolerance, high entropy alloys (HEA) may have superior radiation tolerance in their nanocrystalline form. In this study, CoCrFeNiMn HEA samples were processed via high-pressure torsion (HPT) under 6 GPa at room temperature for 1 (1T) and 8 (8T) turns to form nanograins with unsaturated and saturated plastic deformation, respectively. After 3.4MeV Ni ion irradiation at 500 & DEG;C, grain growth was observed in both HPT-processed samples. The microstructural evolution is dependent on pre-irradiation HPT processing, with the 8T sample showing stronger radiation tolerance against dislocation development and hardness changes, observed through transmission electron microscopy and nanoindentation, respectively. This radiation resistance is attributed to a unique nanodomain microstructure formed within the radiation-coarsened grains of the 8T sample. Microstructural and microchemical analysis suggested both HPT process and the alloy chemistry played roles in the nanodomain formation.