Interface study of short mullite fiber reinforced Al-4.5Cu alloy composites

The interest in discontinuously reinforced metal matrix composites has increased extensively in recent years. It is possible nowadays to produce many new cheaper aluminum-based composites such as aluminum borate (Al18B4O44) whisker reinforced ones and aluminosilicate (Al2O3DTSiO2) short fiber reinforced ones at even lower cost. Among various aluminosilicate fibers, short mullite fibers (3Al2O3DT2SiO2) show outstanding properties, which may make this composite a potential candidate for commercial applications in the near future. However, many investigators have indicated that there are severe interfacial reactions between the fibers and the matrix in aluminosilicate and/or crystallized aluminosilicate short fiber reinforced aluminum-based composites, resulting in the formation of MgAl2O4 spinel which tends to be detrimental with the attendant loss of fiber strength and leads to decreases in the properties of the composites. There are also researchers who indicate that MgAl2O4 spinel was not formed at the interface of mullite short fiber reinforced Al-Si alloy (containing Mg) composite. The question is are there any interfacial reactions in short mullite fiber reinforced aluminum-based composites? The answer is YES based upon our recent research work. The results of the present paper are quite different from those of Cao et al. and worth further investigation. The aluminum alloy matrix used in the present work was an Al-4.5Cu binary alloy, having a chemical composition (in wt%): Cu: 4.45, Fe: 0.23, Mn: 0.04, Zn: 0.01 and the balance aluminum.