Microstructure, Mechanical, and Machining Properties of 2024 Al Composites Reinforced with TiB₂, SiC, and Diamond Particles

Particle-reinforced aluminum matrix composites demonstrate remarkable potential for use in aerospace, precision instruments, and electronic packaging applications due to their superior specific strength, high specific stiffness, and low thermal expansion coefficient. However, increasing the reinforcement volume fraction to enhance the elastic modulus often leads to a reduction in plasticity and machining performance. This study investigates hot-pressed 27 vol.% TiB₂/2024, 15 vol.% diamond/2024, and 37 vol.% SiC/2024 composite with equivalent elastic moduli, focusing on the effects of TiB₂ particle size and T6 heat treatment on their microstructure, mechanical properties, and machining performance. The results reveal that increasing the TiB₂ particle size from 7 μm to 25 μm reduces the tensile strength from 397.1 MPa to 371.7 MPa, increases surface roughness values from 110 nm to 177 nm, but simultaneously decreases tool wear. Among the tested composites, the 27 vol.% TiB₂/2024 composite exhibits optimal interfacial bonding without Al₄C₃ formation, providing the most effective load-bearing strengthening, as well as the lowest surface roughness and minimal tool wear. Moreover, the T6 heat treatment further enhanced the tensile strength of the 27 vol.% TiB₂/2024 composite from 397.1 MPa to 421.7 MPa, while reducing the surface roughness values during turning from 110 nm to 79 nm and further minimizing tool wear, thus achieving outstanding overall mechanical and machining performance.