Influence of rotational speed on the formation of friction stir processed zone in pure copper at low-heat input conditions

The aim of this work is to study the influence of rotational speed on the formation of friction stir processing (FSP) zone in commercial pure copper at low-heat input conditions. The experiments were conducted using K-type thermocouples to record the peak temperature history at different locations on the workpiece. The results suggest that the temperature achieved during processing plays an important role in determining the microstructure and properties of the processed metal. FSP produced very fine and homogenous grain structure and it is observed that smaller grain size structure is obtained at lower rotational speed whereas a tunnel defect was formed at lower speed of 250 rpm. It is also observed that the hardness of the processed copper depends strongly on the heat input during FSP. Tensile tests were carried out and the tensile strength of the FSPed samples was compared to that of the base metal. For a successful FSP at low-heat input condition, the minimum rotational speed was found to be 350 rpm.