不同Mg/Si比对含Zn的Al-Mg-Si合金再结晶组织及性能的影响

为改善Al-Mg-Si系合金汽车板综合性能，通过浇铸法制备出3组合金成分铸锭，并经过均匀化、热轧、中间退火、冷轧，获得1 mm厚的合金板材.合金板材经560 ℃固溶30 min后，立即在100 ℃条件下预时效8 h，室温停放14天，模拟铝板转运存储过程，并拉伸变形2%，再在185 ℃下进行20 min烘烤处理，实现烘烤硬化.采用金相显微镜、装备电子背散射衍射的扫描电镜对合金进行显微组织观察及织构分析，通过万能电子试验机进行力学性能测定，研究不同Mg/Si比和高Zn元素对合金再结晶组织及织构、烘烤硬化性以及腐蚀敏感性的影响.结果表明，Mg/Si比相等合金再结晶组织更加均匀细小，平均晶粒尺寸190 μm，存在相对较少的Cube织构{001}<100>和较多的P型织构{011}<122>；高Mg合金、高Si合金局部晶粒粗大，Cube织构{001}<100>较多，P型织构{011}<122>较少；预时效后，Mg/Si比相等合金强度较高，且烘烤硬化性优异，烤漆硬化增量达到107 MPa；烤漆后，更多的Zn原子扩散到晶界上，强化晶界微电流反应，欠时效态Mg/Si比相等合金较高Mg合金、高Si合金抗腐蚀敏感性降低，被腐蚀深度为121 μm.
In order to improve overall performance of automotive sheet of Al-Mg-Si series alloy, three groups of alloy ingots were prepared by casting method, then, 1 mm thick alloy sheets were achieved through homogenization, hot rolling, intermediate annealing, cold rolling. After solution treatment at 560 ℃ for 30 mins, immediately pre-aging at 100 ℃ for 8 h, and then stored at room temperature for 14 days to simulate the process of transportation and storage. Finally, the alloy sheets baked hardening at 185 ℃ for 20 mins after 2% deformation. The microscopic structure of alloy was observed by metallographic microscope; its texture was analyzed by scanning electron microscope equipped with electron back scattering diffraction, and the mechanical property was tested by electronic universal testing machine. The effect of different Mg/Si ratio and high Zn content on recrystallized structure and texture, bake hardenability and corrosion sensibility were studied. The results indicated that the recrystallized structure of alloy with equal Mg/Si ratio was smaller and more uniform. The average size of grains was 190 μm. The cube orientation {001}<100> was smaller, while the P orientation {011}<122> was larger. Whereas the local grains of alloys with high Mg content and high Si content were coarse, the cube component {001}<100> was larger and the P component {011}<122> was smaller. The strength of alloy with equal Mg/Si ratio was higher, accompanied by good bake hardenability after pre-aging. The paint-bake hardening increment was 107 MPa. After bake hardening, more Zn atoms were diffused into grain boundary, enhancing the response of micro-current. The resistance of corrosion sensibility was poorer than that of high Mg content and high Si content alloy. The depth of corrosion was 121 μm.