Effects of Cu Contents on Mechanical Properties of Al-Si-Mg-Er-Zr Alloy at Room Temperature and High Temperature

The effect of Cu content on the tensile properties of Al-Si-Mg-Er-Zr alloy at room temperature and high temperature was studied. Results show that there are alpha-Al, Si, fi , Q and 9 phases in the as-cast Al-Si-Mg-Er-Zr alloys with different Cu contents. With the increase in Cu content, the eutectic microstructure of the alloy increases, and it is bone-shaped, which is conducive to improving the casting performance of the alloy. With the increase in Cu content, the yield strength of as-cast alloys increases. Three Al-Si-Mg-Er-Zr alloys with different Cu contents (0.6Cu, 1.0Cu and 1.4Cu) were heat treated under 500 degrees C/4 h+ 540 degrees C/2 h+18 0 degrees C/x h, and they reach peak aging at 10, 12 and 12 h with the peak hardness (HV) of 1344.6, 1364.2 and 1398.5 MPa, respectively. With the increase in Cu content, the room temperature tensile strength of the alloys under T6 temper increases, which is due to the fact that the alloy containing 1.4% Cu has the most strengthening phase, including fi '' phase, Q ' phase and 9 ' phase. After 44 h of soaking at 300 degrees C, the hardness of the alloy containing 1.4% Cu decreases the least. This is because with the increase in the Cu content, the amount of the Q-Al5Mg8Cu2Si6 precipitates increases, and the Q-Al5Mg8Cu2Si6 phase is the main thermo-dynamically stable precipitate at 300 degrees C, improving the heat resistance of the alloy. The elongation at 300 degrees C of the three Cu alloys under T6 temper is higher than that at room temperature, and the fracture form also changes from brittle fracture at room temperature to ductile fracture at 300 degrees C.