Enhancing grain refinement in polycrystalline materials using surface mechanical attrition treatment at cryogenic temperatures

The surface mechanical attrition treatment (SMAT) process was applied to pure Cu at both cryogenic and room temperatures. The cryogenic SMAT process resulted in a 60% reduction of grain size in the polycrystalline microstructure compared to that at room temperature. The level of grain refinement is related to a transition in the dominant deformation mechanism during SMAT from a dislocation-mediated behavior at room temperature to a twinning/shear band-mediated behavior at cryogenic temperatures, which also helps to suppress thermally activated processes.