采用力学性能测试、DSC及TEM研究了预变形对Al-Mg-Si-Cu合金析出行为的影响. 结果表明, 在慢速率升温过程中, 预时效态合金GP区溶解速率均随预变形量的增加而降低, 利用Avrami-Johnson-Mehl方法求得经0, 5%和15%预变形后合金的GP区溶解激活能分别为137.1, 189.5和141.3 kJ/mol; 若合金经不同预变形后直接进行185 ℃, 20 min烤漆硬化, 预变形可有效促进沉淀相析出, 提高烤漆硬化增量, 最高达160 MPa, 不过预变形量大于10%时合金烤漆硬化增幅减缓; 此外, 经预变形处理后烤漆态合金的GP区溶解速率在一定温度下均较低, 但高于某一温度后, 相应的GP区溶解速率均高于未经预变形处理, 最终获得的ln[(dY/dT)φ/f(Y)]-1/T曲线甚至会出现高激活能向低激活能转化现象; 不过随预变形量增加, β′′相析出激活能不断降低, 析出速率不断增加.

To reduce the weight of car body, Al-Mg-Si-Cu alloys have been widely used to produce outer body panels of automobiles due to their favorable high strength-to-weight ratio, corrosion resistance, weldability and good formability. Al-Mg-Si-Cu alloys belong to age-hardenable aluminium alloys, whose strength derives mainly from the matrix precipitation during aging treatments. However, their bake hardening response still need to be further improved to enhance their dent resistance. A novel thermo-mechanical treatment consisting of conventional pre-aging, pre-deformation and re-aging was developed to enhance the tensile properties and bake hardening increment of Al-Mg-Si-Cu alloys. In this work, the effect of pre-deformation on the precipitation behaviors of Al-Mg-Si-Cu alloy was studied by DSC, mechanical property measurement and TEM. The results show that, the GP zone dissolution rate decreases with increasing pre-deformation during the slow heating up process for the pre-aged alloy, the corresponding activation energies of 0, 5% and 15% pre-deformed alloy calculated by Avrami-Johnson-Mehl method are 137.1, 189.5 and 141.3 kJ/mol, respectively. If the pre-deformed alloys are directly bake hardened at 185 ℃ for 20 min, precipitation and bake hardening increment can be greatly improved by pre-deformation (the highest bake hardening increment is 160 MPa), but the bake hardening increment rate gradually decreases if the pre-deformation is above 10%. In addition, the GP zone dissolution rates of pre-deformed alloys after bake hardening treatment are much lower when the heat treatment temperatures are below one certain value, but if the treatment temperatures above it, the corresponding GP zone dissolution rates are higher than that of alloy without pre-deformation, finally, the activation energy changes from high value to low value even can be observed in the ln[(dY/dT)φ/f(Y)]-1/T curve. For the precipitation in the alloys, with increasing pre-deformation, its activation energy gradually decreases, corresponding gradually increase of precipitation rate.