Microstructure and mechanical properties of an Al-Ni-Co intermetallics reinforced Al matrix composite

A new intermetallic particle reinforced metal matrix composite was produced from pure Al and 15 wt% Al₇₂Ni₁₂Co₁₆ quasicrystalline particles by stir-casting method, followed by hot-extrusion. Microstructural analysis of the as-cast composite shows that the Al ₇₂Ni₁₂Co₁₆ quasicrystalline phase has transformed to the crystalline phase Al₉(Co, Ni)₂ and an eutectic structure has formed in the Al matrix during the casting process. The particle size of the Al₉(Co, Ni)₂ phase is much smaller than that of the original quasicrystalline particles. After extrusion, the composite has a more uniform distribution of the reinforcement particles and eutectic structure as well as a reduced porosity. Tensile tests indicate that the mechanical properties of the as-cast composite are improved over the matrix properties remarkably, except for the ductility. The strength and ductility of the composite can be improved by the hot-extrusion, while the elastic modulus can be slightly decreased.