Effects of Reinforcement Volume Fraction on Mechanical Properties and Microstructures of 7075Al Matrix Composites Reinforced by FeCoCrNiAl High-Entropy Alloy Particles

High-entropy alloy particles reinforcements improve the mechanical properties of aluminum matrix composites while increasing its density. Investigating the effects of the reinforcement content is conducive to the fabrication of lightweight and high strength composites. FeCoCrNiAl high-entropy alloy particles (HEAp) reinforced 7075Al matrix composites (HEAp/Al) with different HEAp volume fractions of 5, 10, 15, and 20 vol% were fabricated via a vacuum ball milling and vacuum hot pressing sintering, and then the microstructures, interface, density, and mechanical properties of the HEAp/Al composites were characterized. The results indicated that composites with high relative density can be obtained with a holding time of 10 min at 580 °C, 30 MPa; the HEAp distribution was homogeneous as the increase of reinforcement volume fraction decreases and forms agglomeration, especially when the volume fraction is up to 15 vol% and 20 vol%; the density and hardness of HEAp/Al composites improved with the increase of reinforcements’ volume fraction, whereas the flexural strength and fracture toughness of HEAp/Al composites increased at first and then decreased; the HEAp/Al composites reinforced by 10 vol% HEAp showed the maximum flexural strength and fracture toughness, which were increased by 124.6% and 107% compared with 7075Al, respectively; the improvement of mechanical properties was attributed to the dislocation strengthening behavior and load transfer effect of the HEAp reinforcement