CoCrFeNiMoTi High-Entropy Alloy Reinforced Mg Matrix Composites Produced by Multi-pass Friction Stir Processing: Focus on Pin Geometry, Microstructure and Mechanical Properties

In the present study, the effect of pin geometry of friction stir processing (FSP) on microstructure and mechanical properties of a novel magnesium matrix composite reinforced with CoCrFeNiMoTix high-entropy alloy (HEA) particles was investigated. Microstructure results indicated uniform distribution of HEA reinforcements and significant grain refining (reduction from 17.1 to 1.3 µm) in the composite processed with triangular pin. Maximum hardness and compressive strength were obtained as 111 HV and 219 MPa in the composite processed by triangular pin. Non-uniform distribution of HEAs in the composite processed by conical tool was a main factor for decreasing the mechanical properties. A comparative plot indicated good performance of HEA reinforcements in hardness improvement of the Mg matrix composites processed by FSP as compared with conventional reinforcements.