Effects of heat treatment on microstructure and the fracture toughness of SiCp/Al alloy metal matrix composites

The current study focuses on the fracture toughness behaviour of A359 aluminium matrix reinforced with 31 wt. % SiC particulates subjected to different heat treatment conditions. Unreinforced aluminium alloy fracture properties have been also determined for reference purposes. Three different heat treatment conditions have been applied to the Al/SiC p composites and the fracture toughness values have been determined for all specimens. Infrared thermography was used to monitor the plane crack propagation behaviour of the materials and validate the fracture toughness testing. As expected, the obtained K IC values were found to be lower than those of the unreinforced matrix alloy. However, heat treatment considerably improved the fracture toughness of the composites. In particular, the specimens heat treated under the T6 condition exhibited enhanced fracture toughness compared to the other two conditions. This behaviour can be attributed to a mechanism related to alterations in the microstructure at the vicinity of the interface induced by the heat treatment. This mechanism was associated with precipitates accumulated at the interfacial region resulting in material hardening.