It was noted that the surface mechanical attrition treatment technique had been developed in order to synthesize a nanostructured surface layer on metallic materials. The grain refinement process during surface mechanical attrition treatment was investigated here in materials (Inconel 600, AISI304), having low stacking fault energies, by means of transmission electron microscopy and high-resolution electron microscopy, respectively. In Inconel 600, grain sub-division was caused by the interaction of mechanical micro-twins with dislocations. In AISI304, with a lower stacking fault energy, twin-twin intersections sub-divided the initial grains into refined blocks ranging from nm to sub-μm in size. These grain sub-division processes, involving the interaction of micro-twins with dislocations or micro-twins, differed from those observed in high stacking fault energy materials; where dislocation interactions predominated in grain refinement.

Development of Nanostructures in Metallic Materials with Low Stacking Fault Energies during Surface Mechanical Attrition Treatment. N.Tao, H.Zhang, J.Lu, K.Lu: Materials Transactions, 2003, 44[10], 1919-25