Effect of Rotational Speed on Microstructure and Properties of Al-Based Composite Reinforced with High-Entropy-Alloy Particles Fabricated by Friction Stir Processing

In the present investigation, the production of composites based on 7075Al is involved, reinforced with particles of high-entropy alloy (AlCoCrFeNi), using the friction stir processing (FSP) technique. The primary objective is to examine how varying the rotational speed during processing affects the uniformity of the composite microstructure, the strength of the bonding between different materials, and the mechanical properties of the composite. In these findings, it is indicated that higher processing rotational speeds lead to enhanced homogeneity of the composite material and promote strong bonding with the matrix. The Al13Co4 phase is generated at the interface before the formation of the Al5Co2 phase. The microhardness of the composites exhibits an increase in hardness of 78%, 84%, 86%, and 83% compared to the hardness of the 7075Al. Similarly, the tensile strength is enhanced by 26%, 36.7%, 49%, and 40%, respectively. The broken surface shows an even spread of particles with many small depressions, which is a clear sign of a common type of fracture that can stretch without breaking. The primary processes that enhance the strength of the FeCoNiCrAl/7075Al composite manufactured by FSP include the load-transfer effect, dispersion strengthening, grain refinement strengthening, and thermal mismatch strengthening.