Microstructure and thermal expansion of Ti coated diamond/A1 composites

A titanium coating fabricated via vacuum vapor deposition for diamond/Al composites was used to improve the interfacial bonding strength between diamond particles and Al matrix, and the Ti coated diamond particles reinforced Al matrix composites were prepared by gas pressure infiltration for electronic packaging. The surface structure of the Ti coated diamond particles was investigated by XRD and SEM. The interfacial characteristics and fracture surfaces were observed by SEM and EDS. The coefficient of thermal expansion(CTE) of 50% (volume fraction) Ti coated diamond particles reinforced Al matrix composites was measured. The Ti coating on diamond before infiltration consists of inner TiC layer and outer TiO₂ layer, and the inner TiC layer is very stable and cannot be removed during infiltration process. Fractographs of the composites illustrate that aluminum matrix fracture is the dominant fracture mechanism, and the stepped breakage of a diamond particle indicates strong interfacial bonding between the Ti coated diamond particles and the Al matrix. The measured low CTEs (5.07×10⁻⁶−9.27×10⁻⁶K⁻¹) of the composites also show the strong interfacial bonding between the Ti coated diamond particles and the Al matrix.