The effect of coarse and fine Ti₃SiC₂ particle reinforcement in aluminum matrix composites

Metal matrix composites (MMCs) reinforced by MAX phases are a promising class of advanced materials that exhibit high mechanical strength, wear resistance, and fracture toughness. Compared to MMCs reinforced with conventional ceramic particles, MAX phases do not hinder machinability or electrical and thermal conductivity of the metal matrix. This study investigated the effect of adding 3, 9 and 18 wt% coarse- and fine-sized Ti₃SiC₂ particles to pure Al. The Ti₃SiC₂/Al composites were fabricated by spark plasma sintering at a relatively low temperature of 540 °C, preventing the decomposition of the MAX phase and retaining its unique layered structure. It was found that the fine MAX particles hindered the sintering process. A high fraction of fine particles resulted in abundant porosity, weak interfaces and deteriorated mechanical properties. The microstructural analysis revealed a homogenous microstructure with the residual porosity being located mostly at grain boundaries near Ti₃SiC₂–Al interfaces. In addition, thin oxide layers could be observed at some of the Ti₃SiC₂–Al interfaces, which can aid in facilitating bonding between Al and Ti₃SiC₂. The composites with mostly coarse particles exhibited superior mechanical properties. The hardness increased with the addition of MAX particles and was shown to be slightly anisotropic, and the highest bending strength was achieved for the 3 wt% Ti₃SiC₂/Al. Nanoindentation hardness mapping analysis shed some light on the strengthening mechanism. The results of this study can serve as a basis for further research utilizing MAX-phase particle reinforcements in MMCs.