Effect of pre-aging treatment on microstructure and properties of an Al-Mg-Si-Cu alloy

Effect of pre-aging process parameters on microstructure and mechanical properties of an Al-Mg-Si-Cu alloy were investigated using TEM and tensile test.The results show that the pre-aging treatments at 80-(200 ℃) can suppress the negative effect of natural aging on subsequent paint-bake cycle.After pre-aging at(80 ℃) for 2-30 min,the improvement of strength for the alloy after paint-bake treatment is not significant.Meanwhile,the alloy pre-aged at 120 to(160 ℃) for 5 to 10 min exhibits a relative low yield strength and good ductility in T4P state,which is favorable for stamping,and after the paint-bake treatments the high strength of the alloy is obtained.The strength of the alloy at T4P and T8X conditions is further increased when it is pre-aged at(200 ℃.) The size of GP zones at T4P condition has a crucial influence on the improvement of paint-bake response of the alloy.