Friction stir processing of high-entropy alloy reinforced aluminum matrix composites for mechanical properties enhancement

Metal matrix composites have been developed to overcome the urgent demand of light-weight design. High entropy alloys (HEAs) are newly emerged as a new kind of potential reinforcement for metals due to their outstanding physical and mechanical properties. Here, a kind of novel Al matrix composite reinforced by Al_0.8CoCrFeNi HEA particles was fabricated by multi-pass friction stir processing (FSP). The incorporated HEA particles were homogeneously distributed into the composites and maintained the structural integrity. The average grain size of the FSPed composites decreased from 4.6 μm of Al matrix to 2.8 μm due to the particle-stimulated nucleation mechanism. The hardness, yield strength and ultimate tensile strength of the FSPed composites increased by 56%, 42% and 22% than that of the FSPed Al matrix with no obvious decrease of elongation. Interfacial diffusion occurred and the interfacial region is confirmed to be the Al₃CoCrFeNi rather than the intermetallic phases. HEA particles have great potentials in mechanical properties enhancement for conventional light-weight alloys.