Effect of friction stir process parameters on the mechanical properties of 5005-H34 and 7075-T651 aluminium alloys

The properties and microstructure of friction stir processed AA 7075-T651 (Al-Zn-Mg-Cu) Aluminium alloy were studied using various tool designs. Trials were conducted on AA 5005-H34 with the aim of determining the most suitable FSP tool design out of the considered three different pin designs. Fully recrystallised fine microstructure and a defect free processed zone was achieved through the use of some of the FSP pin designs. For FSP 5005-H34 aluminium alloy substantial grain refinement was detected. The initial 192 µm pancake-like microstructure in the AA 5005-H34 base material was refined to 10–20 µm in the processed regions. Similarly, the grain size of around 50 µm in the base material was decreased to 4–10 µm in the processed regions of the FSP of 7075-T651 aluminium alloy. The traverse speed has a greater influence on the microhardness and mechanical properties, compared to the tool rotational speed. Microhardness and mechanical properties were improved as the traverse speed increased, due to the reduction in the precipitate-free zones at the grain boundaries.