Effect of Heat Treatment and Zn Addition on Microstructure and Properties of Al–Si–Cu–Mg–Cr–B Alloy

Zinc-modified hypoeutectic Al–Si–Cu–Mg–Cr–B alloy underwent a two-stage solution treatment at 520 °C for two hours and 550 °C for half an hour, followed by a two-stage aging treatment at 100 °C for three hours and 180 °C for eight hours. The impact of heat treatment and Zn addition on the eutectic Si phase, alloy compounds, and mechanical properties of the hypoeutectic Al–Si–Cu–Mg–Cr–B alloy was systematically investigated using an optical microscope, X-ray diffractometer, scanning electron microscope, energy spectrum analysis, and mechanical properties test. The findings revealed that heat treatment and Zn addition improved the size, morphology, quantity, and types of eutectic silicon phases and alloy compounds, as well as their mechanical properties. After heat treatment, the alloy displayed optimal characteristics with the addition of 0.3 wt% Zn. The eutectic Si phase of the alloy exhibited the most favorable morphology, the greatest variety of alloy compounds, the most favorable morphology and size, and the largest Q index, which is utilized to evaluate the overall tensile properties of the alloy. This indicates superior mechanical properties.