Effect of Cu addition on the microstructure, mechanical and thermal properties of a piston Al-Si alloy

Piston Al-Si alloys are widely used for high-temperature applications especially in automotive industry. Copper is one of the most important elements for improving the strength at room and elevated temperatures. Other effects of Cu addition need to be taken into account as well, i.e. the changes in microstructure and the coefficient of thermal expansion (CTE). We studied the effects of Cu addition to an AA4032 piston alloy on its structure and properties. Thermal analysis, metallography, thermodynamic calculations, hardness, tensile and dilatometer tests were conducted. The results showed that increased Cu addition promoted the formation of primary Si particles in this Al-Si alloy and enlarged its solidification range. The increase of Cu concentration from 1 to 3.5 wt% improves hardness, tensile properties, and CTE of the near-eutectic Al-Si alloys. This work contributes to deeper understanding the role of Cu in Al-Si piston alloys