Effect of iron and copper on the microstructure and mechanical properties of gravity Die-cast Al-Si-Ni-Mg alloys

The microstructure and mechanical properties of gravity die-cast experimental Al-Si-Ni-Mg alloys with varying addition of recycled Cu wire and Fe pick-up from mild steel crucible and tools was investigated. Addition of Cu and Fe in the as-cast experimental alloys, improves the tensile strength by 6.11%. Yield strength increases marginally by 3.43% up to 1.07 wt.% of iron and 2.98 wt.% of copper and then decreases. Relative percentage elongation drops significantly by 89.38%. A very small drop in impact strength was observed. The positive influence of copper and iron addition in the Al-Si-Ni-Mg alloy system due to fine grain strengthening and delay in the formation of hard plat like beta-Al5FeSi phase, iron bearing inter-metallic phase (beta-Al5FeSi) found only when iron content reaches 1.07 wt.%. X-ray Diffraction, optical microscope (OM) were used to characterize the material.