Abstract
Thermal cycling test was carried out for 20 vol% and 40 vol% SiC particle/Al-4 mass%Cu alloy composites to evaluate the bonding strength of the SiC particle/matrix interface in PRMMC fabricated by a low-pressure infiltration process (LPI process). The SiC particles were distributed homogenously in the specimens and a reaction layer of less than 1 μm thickness was observed at the SiC particle/matrix interface before thermal cycling test. This reaction layer was identified as Al4C3 formed by the reaction between the alloy melt and SiC particle during infiltration. The θ phase, which might form a coherent interface with Al4C3, crystallized around the SiC particles through the Al4C3 layer. The coefficient of thermal expansion was hardly changed during thermal cycling for both the 20 vol% and 40 vol% SiC particle/Al-Cu composites. No significant change in the microstructure and no detachment at the SiC particle/matrix interface were observed after thermal cycling test. The interfacial structure consisting of SiC, Al4C3, θ phase and α-Al in order was considered to exhibit a strong bonding of SiC particles to the matrix. The Vickers microhardness measured on the SiC particles in the specimens having a strongly bound interface show hardness values with a small scatter, while those for the specimens having a weakly bound interface exhibit a large scatter in the hardness values. It is suggested that the bonding strength of the reinforcement particle/matrix interface could be evaluated qualitatively from the Vickers microhardness test.
