固溶处理对7449铝合金激光焊接接头组织和性能的影响

Effect of solution treatment on microstructure and properties of laser welded joints of 7449 aluminum alloy

通过激光焊接方法对7449铝合金进行焊接,并对焊接接头整体进行焊后固溶处理。运用光学显微镜(OM)、扫描电镜(SEM)、显微维氏硬度计、疲劳试验机等方法对固溶处理前后的焊接接头进行显微组织观察以及宏观力学性能表征。结果表明,7449铝合金激光焊接接头在固溶处理之后,其接头组织分布更加均匀,晶粒尺寸略有增大,第二相粒子明显减少;拉伸时,固溶处理前后焊接接头的断裂位置均在焊缝和熔合线附近;固溶处理前后焊接接头的抗拉强度分别为268.4 MPa和425.6 MPa,焊接接头的平均显微硬度分别为111.2 HV20和141.8 HV20;经固溶处理后,焊接接头的断裂方式由固溶处理前的沿晶断裂变为韧性断裂。

Solution treatment was carried on 7449 aluminum alloy welded joints by the way of laser welding. The microstructure and macro- mechanical properties of the welded joints before and after solution treatment were investigated by means of optical microscope （ OM ） , scanning electron microscope（SEM） , micro-vickers and fatigue testing machine. The results show that after solution treatment, much more homogeneous microstructure of the welded joints is obtained, but the grain size increases slightly. In addition, the second phase particles are significantly reduced. After tensile test, the fracture positions of the welded joints before and after the solution treatment are both in the vicinity of the welded bead and fusion line, and the tensile strength and the average micro-hardness of the welded joints are 268.4 MPa, 425.6 MPa, and 111.2 HV20, 141.8 HV20, respectively. Meantime, the fracture mode of the welded joints transfers from intergranular fracture to ductile fracture.