Microstructure and Mechanical Properties of Al/Cup/SiCp/TiCp-Based Hybrid Composites Fabricated by Spark Plasma Sintering

Aluminum-based hybrid composites with new combinations of both hard ceramic particulates (5-10 wt.% SiC and 5-10 wt.% TiC) and ductile metallic (27 wt.% Cu) reinforcements are successfully synthesized via spark plasma sintering route to achieve significantly high specific hardness and specific modulus. The synthesized hybrid composites exhibit an adequate consolidation with marginal porosity and a clean particle–matrix interface, ensuring better particle–matrix bonding. Detailed microstructural characterization by electron microscopy and X-ray diffraction analysis further reveals that metallic copper particles could be successfully incorporated with marginal intermetallic formation by the interfacial reaction. Mechanical properties have been evaluated by macro-hardness and depth-sensing nano-indentation measurements. Among the fabricated ones, the Al-27wt.% Cup-5wt.%SiCp-5wt.% TiCp hybrid composite exhibits impressively high specific hardness (35 VHN/gcm−3), specific Young's modulus (33.9 GPa/gcm−3), and very high bulk modulus (28.2 GPa/gcm−3) when compared with the Al-based composites reported in the literature. This is attributed to the evolution of a novel microstructure consisting of SiC, TiC, and Cu particulates in a highly sub-structured aluminum-based matrix with a significant amount of dislocation density (6.6×1014 m−2). The elasto-plastic characteristics of the matrix are further explored through the depth-sensing nano-indentation technique.