The influence of tool shape on the microstructure evolution and tribological properties during friction stir processing of AlCoCrFeNi high entropy alloys particle reinforced AA7075 aluminum alloy

This research involved reinforcing the AA7075 Al alloy with AlCoCrFeNi high-entropy alloy particles using Friction Stir Processing (FSP). The relationship between tool geometry and the changes in microstructural and tribological features after FSP is analyzed. Two distinct tool shapes, single and dual-pin tools, were the main focus of the study due to their significant influence on material flow. We observed that the tool's design positively influenced the microstructure and wear characteristics. Microstructural observations indicated that the utilization of a double-pin tool as an additional source of energy is a valuable alternative to the single-pin tool during FSP. The grain size reduction was notably affected by the dual-pin tool from 9.10 μm to 7.20 μm, resulting in a remarkable enhancement in the AlCoCrFeNi particle distribution across the matrix that can be attributed to the surplus plasticity and improved material flow. The results also revealed an improvement in the shear punch strength (SPT) as well as wear resistance and friction coefficient of the AA7075/AlCoCrFeNi surface composite.