Forming Nanocrystalline Surface Layers in Copper Using Friction Stir Processing

Abstract

In the present work, a nanostructured layer was formed on the surface of pure copper via friction stir processing (FSP). The surface nanostructuring can be of significant importance in terms of surface-dependent properties such as fatigue, wear, coating, and even corrosion. During FSP, the applied rotating and traverse speeds were 1600 rpm and 50 mm/min, respectively. The results show that a nanograin layer of about 90 µm thick, having the grain size of 50–200 nm, was formed on the surface of pure copper. The nanostructured layer was then characterized using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), as well as scanning electron microscopy (SEM). The microhardness of nanograin layer (175 Hv) was about three times that of the base material (60 Hv).