Elemental redistribution in a nanocrystalline Ni–Fe alloy induced by high-pressure torsion

Abstract

• Elemental distribution of a nc Ni–Fe alloy before and after high-pressure torsion. • The supersaturated Ni–Fe solid solution was stable under HPT. • C and S atoms further segregated to the remaining GBs during grain growth. • GB diffusion and the motion of defects facilitate the elemental redistribution. An electrochemically deposited nanocrystalline supersaturated face-centred-cubic Ni–21 at.% Fe alloy with an initial average grain size of ∼21 nm was processed using high-pressure torsion (HPT) that resulted in grain growth via grain rotation and coalescence to an average grain size of ∼53 nm. Atom probe tomography investigations revealed that the supersaturated Ni–Fe solid solution was stable under HPT and that C and S atoms, which are the major impurities in the material and segregated to the grain boundaries (GBs) of the as-deposited material, migrated from disappearing GBs to the remaining GBs during HPT. We propose that the elemental redistribution was facilitated by GB diffusion and the motion of a large volume of HPT-induced defects at the GB regions during the grain growth process. This elemental redistribution process is different from other HPT-induced elemental redistribution processes reported in the literature.