EFFECTS OF ALLOYING ELEMENTS ON THE SINTERING AND HEAT TREATMENT OF ELEMENTALLY MIXED ALUMINUM POWDER ALLOYS

摘要

The individual and combined effects of various alloying elements in aluminum powder compacts were studied in regards to the sintered and heat treated properties. In binary aluminum mixtures, copper formed a persistent liquid phase with aluminum and effectively raised the sintered density and transverse rupture properties, whereas magnesium or zinc formed a transient liquid phase and lowered the density and the properties. In Al-6%Cu base ternary systems, zinc addition improved the sintered properties to some extent but the heat treated properties more significantly. Since the globules of the solidified liquid phase contain a large portion of CuAl_2 phase, which is much harder and more brittle than the matrix, they can act as reinforcing particles in the soft aluminum matrix. The large increase of strength along with the reduction of ductility and also the significant improvement of wear resistance obtained with 6% or more Cu addition are thus attributed to the reinforcing effect of the solidified liquid phase.