Microstructure and mechanical properties of AlNbTaZr-Al2O3 refractory high entropy alloy reinforced Al6061 metal matrix composite

Traditional ceramic-reinforced Metal Matrix Composites (MMCs) often exhibit challenges such as weak interfacial bonding, ceramic particle fragmentation, and thermal expansion mismatch, which collectively compromise their plasticity and toughness. To overcome these limitations, the present study investigates a novel composite system by reinforcing Al6061 matrix with AlNbTaZr-Al₂O₃ Refractory High Entropy Alloy (RHEA) powders which were fabricated through mechanical alloying for 30 h. The research focuses on analyzing the structural evolution, mechanical properties, and wear behavior of the resulting Al6061–AlNbTaZr–Al₂O₃ composite. X-ray diffraction (XRD) confirms progressive nano structuring of RHEA powders with increased milling duration. Transmission Electron Microscopy (TEM) reveals an average grain size of 246.7 nm, with a maximum of 385.1 nm. Optical microscopy shows pronounced grain refinement in the composite, attributed to Dynamic Recrystallization (DRX) induced by RHEA particles. Mechanical testing demonstrates a 69.4 % increase in tensile strength for the composite (164.2 MPa) compared to pure Al6061 (96.9 MPa), and a substantial enhancement in ultimate compressive strength (326.6–335.3 MPa vs. 236.1 MPa). Tribological analysis reveals a lower and more stable coefficient of friction (0.45–0.55) than Al6061 (0.57 at 20 kN), reflecting improved wear resistance due to reduced material removal and the reinforcement effect of the RHEA phase. Based on the results, the Al6061–AlNbTaZr–Al₂O₃ composite exhibits significantly enhanced mechanical strength, refined microstructure, and superior wear resistance, making it a promising candidate for structural and tribological applications in aerospace, automotive, and defense industries where lightweight, high-strength, and wear-resistant materials are essential.