Study on microstructure and mechanical properties of (TiC+B4C)/6061Al composites prepared by vacuum hot-press sintering method

Abstract

The vacuum hot-press sintering method combined with hybrid particle reinforcement design represents an innovative approach to developing aluminum matrix composites. This study details the design and development of a new vacuum hot-press sintering device for aluminum matrix composites. The 6061Al hybrid reinforced with varying TiC+B₄C content (0, 10, 20, and 30 wt%) was systematically investigated utilizing wet mixing followed by vacuum hot-press sintering at 580 °C and 30 MPa, and a novel hybrid reinforcement model was developed. Results indicate that owing to the doping of B₄C, diffusion of B and C was observed in the (TiC+B₄C)/6061Al composites. The distribution characteristics of the Mg₂Si phase were changed significantly, and C in B₄C reacted with Si in 6061Al to form SiC in situ. The doping effect of B₄C intensified with increasing particle content. As the TiC+B₄C content increased, the refinement effect on the grain size of 6061Al enhanced, and the improvement in hardness and strength of the (TiC+B₄C)/6061Al composites strengthened. The grain size refinement and the hardness increase of the materials with 30 wt% TiC+B₄C content were close to 22 % and 102 %, respectively. The strength of the materials with different contents of TiC+B₄C were 165 ± 2 MPa, 199 ± 3 MPa, 212 ± 5 MPa, and 230 ± 3 MPa, respectively. Unlike the fracture mode observed in unreinforced 6061Al, the fracture mode of the (TiC+B₄C)/6061Al composites was a hybrid fracture mode of ductile fracture of the 6061Al matrix and cleavage fracture of the particles, and the proportion of cleavage fractures increased gradually with the increasing TiC+B₄C content. This study can shed light on designing new aluminum matrix composites.