Strain-enhanced diffusion of Cr in nanostructured IF steel under surface mechanical rolling treatment

Abstract

A nanostructured surface layer was produced on IF steel by means of surface mechanical rolling treatment (SMRT). Subsequently, the diffusion behavior of Cr was studied in the nanostructured surface layer under deformation by depositing a thin Cr coating and re-submitting to SMRT. The results revealed that an ultra-high diffusion coefficient (∼2.9 × 10⁻¹⁶ m² s^-1) is achieved at room temperature, resulting in the formation of a (Cr, Fe) solid solution transition region between Cr coating and nanostructured substrate. The extra-fast diffusion should be induced by the high strain and strain rate exerted by SMRT, as well as the existence of various grain boundaries, in the near surface layer of IF steel.