Effects of In Situ TiB2 Particles and (Ce + Yb) on the Microstructure and Mechanical Properties of Al–Si Matrix Composites

In the present work, the in situ TiB2 particle-reinforced Al–Si matrix composites with or without (Ce + Yb) were fabricated by mixed salt–metal reaction, and the effect of TiB2 and (Ce + Yb) on microstructure and mechanical properties were investigated. The results showed that the combined addition of 0.4 wt% (Ce + Yb) and 3 wt% TiB2 further facilitated the uniform microstructure and modified the eutectic Si of composites. Meanwhile, the combined addition of (Ce + Yb) promoted the nucleation and inhibited the growth of TiB2 particles. The mechanical properties of the composites with 0.4 wt% (Ce + Yb) and 3 wt% TiB2 reached maximum values with ultimate tensile strength, yield strength and elongation of 240.5 MPa, 169.8 MPa and 6.6%, which were 53.8%, 116.1% and 164.0% higher compared to the Al–Si matrix alloy. The fractography observations indicated that the fracture mode of the composites belongs to a typical of mixed brittle–ductile fracture. But the combined addition of (Ce + Yb) is beneficial to improve the plasticity of the composites.