Effect of copper and solidification conditions on the microstructure and mechanical properties of Al-Si-Mg alloys

In this research, copper has been used in the ternary system of Al-Si-Mg alloy in different solidification conditions to increase the mechanical properties of the existing alloys. Copper in the range of 0.2-2.5 wt.% has been used in A356 aluminum alloy and cast at different solidification conditions. Sand, graphite, copper and cast iron molds have been designed and manufactured to produce tensile test specimens at different cooling rates during solidification of the alloys. The microstructures of the alloys have been studied through optical and scanning electron microscopy (SEM). Mechanical properties of different alloys at various solidification conditions have been investigated in both non-heat treated and heat treated conditions. The fracture surfaces of the tensile test samples have been studied. All intermetallic compounds formed during solidification have been investigated through SEM-EDS. A new alloy has been developed. It has been found that the best mechanical properties obtained with about 1.5 wt.% copper in Al-Si-Mg alloys solidified in the graphite molds. (C) 2004 Elsevier B.V. All rights reserved.