High-temperature surface alloying of nanocrystalline nickel produced by surface mechanical attrition treatment

A nanocrystalline surface layer is synthesized in Ni by surface mechanical attrition treatment (SMAT). The characterization of microstructure and composition indicates that foreign elements from hardened balls can permeate and diffuse into the surface layer during SMAT, which can further diffuse and homogenize in the surface layer when annealing at high temperature, leading to formation of new alloy. Foreign elements permeating into the surface layer during SMAT followed by diffusing and homogenizing at high temperature provide an alternative effective technology for surface modification.

Research highlights▶ The primary aim of this manuscript is to investigate the effect of annealing process on the diffusion of foreign elements permeated into the nanocrystalline Ni surface layer and its influence on the composition and structure of surface layer. ▶ The results indicate that foreign elements from the hardened balls can be pressed and diffused into the surface layer during SMAT, resulting in the concentrated distribution in the treated surface. In the course of subsequent annealing, foreign elements can further diffuse and homogenize in the surface layer, leading to the formation of new kind of alloy in the surface layer. ▶ Foreign elements permeate into the surface layer during SMAT, further diffuse and homogenize when annealing at high temperature, and finally form the new compound, which can provide an alternative effective technology for surface modification.