Abstract: Transient liquid phase bonding of dissimilar materials of aluminium metal matrix composite (MMC)/low carbon steel was carried out using 50 μm thick commercial copper foil at 590℃ for 30 min and 2h, respectively.The results show that the weak interface is not interlayer/steel interface, but the residual interlayer/MMC interface;the edge of MMC preferentially dissolved by extruded liquid phase leads to a circular notch around faying surface;and the extruded liquid phase spread towards MMC side, but not towards steel side.From the fracture surface, it is known that the joint fracture occurs within the residual interlayer (under lower pressure) or the surface region of MMC (under higher pressure);iron atoms can be remarkably dissolved into interlayer to form intermetallic compounds in metal matrix.Therefore, the joint strengths were low.