Effects of T6 Heat Treatment on Mechanical Properties and Corrosion Behaviors of Al – 9.5Si – 1.5Cu – 0.45Mg Alloy

The effect of the T6 heat treatment mode on the microstructure, mechanical properties and corrosion behaviour of the Al – 9.5Si – 1.5Cu – 0.45Mg (Al – Si – Cu – Mg) alloy was studied. It was found that the most effective T6 heat treatment mode for the Al – Si – Cu – Mg alloy is the following: heating to 490°C with a 5-hour hold, then heating to 530°C with a 4-hour hold and subsequent water quenching, followed by aging at 150°C for 12 hours. In the cast state, the alloy has a tensile strength of 225 MPa and a corrosion depth of 20 μm in a 3.5% NaCl solution. After T6 heat treatment according to the proposed mode, the tensile strength of the Al – Si – Cu – Mg alloy increases to 397 MPa, and the corrosion depth in a 3.5% NaCl solution decreases to 13 μm. The enhancement of strength and corrosion resistance of the alloy after aging is attributed to the spheroidization and refinement of the Si phase, fine 8-Al₂Cu and Q-Al₅Cu₂Mg₈Si₆ precipitates.