固溶处理对7B04-O铝合金搅拌摩擦焊接接头微观组织与力学性能的影响

Effects of Solution Heat Treatment on Friction Stir Welding Joints of 7B04-O Aluminum Alloy

对航空用3 mm厚的带有包铝层的7B04-O铝合金板材进行搅拌摩擦焊接(Friction stir welding,FSW),研究固溶处理对搅拌摩擦焊接接头的微观组织和力学性能的影响。结果表明,当转速为800 r/min、焊接速度为200 mm/min、焊接工具轴肩直径为12 mm时,可得到表面美观、致密无缺陷的搅拌摩擦焊接接头。焊核区发生动态再结晶,形成细小的等轴晶。经固溶处理后,焊核的上部及底部晶粒都发生了异常长大,而中部区域晶粒仍然为细小的等轴晶组织。焊态接头的拉伸试样断裂在母材位置,抗拉强度达到199 MPa,与退火态母材抗拉强度相当,断后伸长率达到12%。在新淬火状态下,接头的抗拉强度为310 MPa,为相同热处理母材的91.4%,断后伸长率为11.2%,试样断裂在焊核区,呈不完全的韧性断裂。

The aero Al-coating 7B04-O aluminum alloy plates with the thickness of 3 mm are subjected to friction stir welding （FSW）, the effect of solution heat treatment on the microstructure and tensile property of the FSW joints are investigated. The results show that, with the rotation rate of 800 r/min, the welding speed of 200 mm/min and the shoulder diameter of 12 ram, sound FSW joints with no defect are obtained. Dynamic recrystallization takeplace in the nugget zones（NZs） with fine and equiaxed grains generated. After the heat treatment, the abnormal growth of grain is found in both the upper and the bottom parts of the NZs, whereas the fine equiaxed grains in the center part is retained. During the tensile test, the fraction position occurs in the base metal of the welded joint. The ultimate tensile strength of the welded joint is 198 MPa, which is equal to that of the base metal, the breaking elongation is about 13.2%. After the solution heat treatment, the tensile strength and breaking elongation of the FSW joint are about 310 MPa and 11.2% respectively, and the joint fails in the NZ during the tensile test, which shows incomplete ductile fracture.