Dry wear behavior of cooling-slope-cast hypoeutectic aluminum alloy

This study investigated the effect of use of a cooling slope on the microstructure, hardness and wear behavior of Al-7Si-Mg alloy. The Al-7Si-Mg alloy was cast with and without a cooling slope at a pouring temperature of 640 degrees C. Examination with optical and electron microscopes showed that the microstructure of cast samples using the cooling slope comprised fine and globular primary alpha-Al phase with homogeneous distribution of eutectic phase, while conventionally cast samples featured coarse and dendritic primary alpha-Al phase. The wear resistance of the cast sample was significantly better with cooling slope casting. The wear mechanism was found to be a combination of adhesion, delamination, oxidation and abrasive wear for both cooling slope- and conventionally cast samples. The wear mechanisms of cast samples both with and without cooling slope are similar and follow Archard's law. The cooling slope-cast samples with fine and globular alpha-Al phase, high hardness and low specific wear rate (K') showed the highest wear resistance of 10.08 x 10(-5) mm(3) N-1 m(-1)