Study on Mg segregation, microstructure evolution and fracture behavior of hot-press sintered (TiC+B4C)/6061Al composites after T4 heat treatment

The T4 heat treatment process is essential for hot-press sintered aluminum matrix composites. This study investigates the evolution mechanism of novel T4 (TiC+B 4 C)/6061Al composites by combining vacuum hot-press sintering with various T4 heat treatments. Results show that due to the addition of B 4 C, in-situ SiC and diffusion of B appeared in T4 (TiC+B 4 C)/6061Al composites. Severe grain boundary segregation of Mg occurred in T4 6061Al, while grain boundary segregation of Mg is noticeably reduced in T4 (TiC+B 4 C)/6061Al composites. Unlike the ductile fracture and intergranular fracture observed in T4 6061Al, fracture in T4 (TiC+B 4 C)/6061Al composites predominantly occurs through ductile fracture of the aluminum matrix and cleavage fracture of particles. During T4 heat treatment, the addition of TiC and B 4 C not only refined the grain size of 6061Al but also promoted the occurrence of static recrystallization of 6061Al. With the increase of solution temperature, the recrystallization volume fraction of the aluminum matrix in T4 (TiC+B 4 C)/6061Al composites first increased and then decreased slightly, the hardness and strength of T4 (TiC+B 4 C)/6061Al composites increased gradually, the plasticity first increased and then decreased. An optimal balance between strength and plasticity in T4 (TiC+B 4 C)/6061Al composites can be achieved at the solution temperature of 530 °C.