Microstructure and Properties of Micro/Nano-Scale (TiB2 + TiC)/Al Composites Prepared by Ti-B4C Reactive Sintering and Spark Plasma Sintering

In this work, micro/nano-scale (TiB2 + TiC)/Al composites with reinforcement contents ranging from 0 to 30 wt.% were fabricated by the combination of Ti-B4C reactive sintering and spark plasma sintering (SPS). The results indicate that a sintering temperature of 1400 °C is essential for achieving a complete reaction between Ti and B4C, successfully producing a bimodal TiB2-TiC reinforcement consisting of nano-scale and micro-scale particles. Microstructure analysis reveals that the addition of micro/nano-scale TiB2 and TiC ceramic particles significantly refines the grain size of the Al matrix from 11.52 μm in pure Al to 1.09 μm in the 30 wt.% (TiB2 + TiC)/Al composite. As the TiB2 and TiC contents increase, Vickers hardness and compressive yield strength increase progressively, while the uniform compressive plastic strain first increases and then decreases. The 20 wt.% (TiB2 + TiC)/Al composite demonstrates the optimal comprehensive properties, with a compressive yield strength of 196.4 ± 6.1 MPa, an ultimate strength of 914.6 ± 20.1 MPa, and a uniform plastic strain of ~73.2%, as well as minimal wear rates of (3.143 ± 0.194) × 10−4 mm3/(N·m), 1.676 ± 0.251× 10−3 mm3/(N·m) and (3.093 ± 0.335) × 10−3 mm3/(N·m) at 1 N, 3 N, and 5 N, respectively. This improvement stems from the combined effects of grain refinement, dispersion strengthening, enhanced load-bearing capacity and reduced adhesive wear via the TiB2 and TiC reinforcements.