Interdiffusion of alloying elements in nanocrystalline Fe–30 wt.% Ni alloy during surface mechanical attrition treatment and its effect on α → γ transformation

A nanocrystalline surface layer is produced in Fe–30 wt.% Ni alloy by surface mechanical attrition treatment (SMAT) and strain-induced nanocrystalline martensite is obtained in the surface layer. The characterization of microstructure and composition indicates that the interdiffusion of Fe, Cr and Ni between the sample and steel balls during the SMAT process increases the starting temperature of the reverse martensitic transformation. The effect of interdiffusion, as a special phenomenon in SMAT, should be noted and utilized.