Microstructural Refinement of Pure Copper by Friction Stir Processing

Recently friction stir processing (FSP) was developed as a generic implement for microstructural modification based on the principles of FSW using a rotating tool inserted in a monolithic work piece which provides frictional heating and mechanical mixing. In this paper, the microstructural evolution characteristics of nugget zone were investigated during friction stir processing (FSP) of pure copper. Pure copper plates were friction stir processed to the depth of 3.4 mm at different process conditions by varying the traverse speed from 30 to 120 mm/min at rotation speeds of 400 and 600 rpm..Defects were observed in rotational speed of 400 rpm. Grain size of NZ depended significantly on plastic deformation and heat input value. By increasing traverse speed at constant rotational speed of 600 rpm grain size of the nugget zone decreased and the hardness increased. Ultimate tensile strength increased with decrease in grain size. FSP was found as an effective method to develop fine-grained microstructure in copper plates.