The interface characterization of the aluminium alloy reinforced with Al2O3 particulates ((Al2O3)p/Al composite) was performed using X-ray diffractometry and energy dispersive X-ray spectroscopy. A layer of MgAl2O4 single crystals was observed at the (Al2O3)p/Al interface in the as-received extruded composites. Such MgAl2O4 crystals formed at the surface of (Al2O3)p are believed to grow by consuming a certain amount of (Al2O3)p. Upon loading, interfacial debonding was observed to occur at the boundary between MgAl2O4 and the aluminium alloy, or along the MgAl2O4 layer itself. These experimental observations are correlated with the tensile properties of such composites.