Effect of (0–40) wt. % Si addition to Al on the thermal conductivity and thermal expansion of diamond/Al composites by pressure infiltration

Abstract

This study pertained to the effect of (0–40) wt.% Si addition to Al on the thermal conductivities (TC) and the coefficient of thermal expansion (CTE) of diamond/Al composites by pressure infiltration. The fracture surfaces and interface microstructures by metal electro-etching were discussed with respect to Al matrix chemistry and diamond particles size. The results revealed that the diamond (single size)/Al–12.2Si (in wt.-pct) composites exhibited higher thermal conductivity of 532 W/m K due to the better interface bonding, which is over 90% of the theoretical prediction by the Hasselman–Johnson Scheme. At the interfaces, SiC was found and the undesired interface formation of Al4C3 was reduced. The CTE of diamond (single size)/Al–40Si (in wt.-pct) composites exhibited the average value of 4.5 × 10−6/K, but the TC value declined to 314 W/m K due to the inhomogeneous enrichment of Si. The bimodal mixtures of diamond particles (106–125 μm: 45–38 μm = 3:1) could improve TC and CTE of composites.