High strength, high thermal conductivity and wear resistance are required for automotive engine piston. It's known that aluminum borate whisker has high strength and good wear resistance and carbon fiber (CF) has high thermal conductivity. In this study, aluminum borate whisker and two types of CFs, which have difference surface structure, PAN-based CF and Pitch-based CF reinforced JIS-AC8A aluminum alloy and AXE522 magnesium alloy are fabricated by squeeze casting. At first, influence of the surface of CF and the matrix on amount of interface reaction product Al4C3 was clarified. Secondly, the influence of Al4C3 amount on the bending strength of the composites was examined. As the results, the bending strength of PAN-based CF composites was higher than that of Pitch-based CF composites. Al4C3 or Al-O-RE compound was identified by TEM and EDX at the interface of PAN-based CF/AC8A or PAN-based CF/AXE522 respectively. Regardless of AXE522 or AC8A matrix, in PAN-based CF composites, large amount of Al4C3 was found compare to Pitch-based CF composites. The bending strength was positively correlated with amount of Al4C3. This suggested that the anchor effect by Al4C3 would contribute to increasing the strength of the composites.
