Effect of Multipass Friction Stir Processing on Structure and Mechanical Properties of CuAl9Mn2 Copper Alloy

This study examines the structure and mechanical properties of CuAl9Mn2 copper alloy processed via friction stir processing. Workpieces, 2 mm thick, were processed using four tool passes. After the initial FSP pass, the stir zone structure was found to be non-homogeneous, with grains changing from equiaxed to elongated in the material flow direction. Grain sizes decreased from 80-140 µm to 3-8 µm. However, after the fourth pass, the stir zone became more homogeneous with equiaxed grains and sizes ranging from 2-6 µm. The increase in microhardness and tensile properties of the material is attributed to the processing temperature, mechanical mixing, and grain refinement. The ultimate tensile strength of the FSP material increased by 13% relative to the metal prior to processing, whether one or four passes were used. Additionally, microhardness in the stir zone increased, which is consistent with the results of mechanical tensile tests.