A356/6005A异种铝合金脉冲MIG焊接接头的组织和力学性能研究

Research on Microstructures and Mechanical Properties of Pulsed MIG Welded Joint of A356/6005A Dissimilar Aluminum Alloy

利用直流脉冲熔化极气体保护焊(metal-inert arc gas,MIG)对A356铸造铝合金和6005A变形铝合金进行对接焊接,并采用光学显微镜(OM)、带能谱的扫描电子显微镜(SEM)、显微硬度及拉伸力学性能测试研究接头的显微组织和力学性能。研究结果表明:A356/6005A焊接接头的断裂位置位于焊缝区,焊接接头的平均抗拉强度为130MPa,屈服强度为102MPa,伸长率为2.1%,焊接系数约为0.43。A356一侧的部分熔化区组织为岛状Al-Si共晶和粗大Si颗粒;焊缝熔化区为典型的Al-Si铸态枝晶组织;6005A一侧的部分熔化区组织有枝晶状和长棒状的Al-Si共晶和Al(Fe,Mn)Si颗粒。接头的硬度随着距焊缝中心距离的增加不断增加,其中,焊缝区的硬度最低,6005A一侧的焊缝硬度高于A356一侧焊缝的硬度。

A356 cast aluminium alloy and 6005 A wrought aluminium alloy were butt welded by direct current pulsed metal-inert arc gas(MIG) welding. The microstructures and mechanical properties of the butt joint were investigated by optical microscopy(OM), scanning electron microscopy(SEM) equipped with energy dispersive spectronmetry(EDS),microhardness and tensile mechanical property testing. The research result shows that the A356/6005 A welded joint mainly fails in welded zone. The average tensile strength, yield strength and elongation of A356/6005 A welded joint are 130 MPa,102 MPa and 2.1%, respectively. And the welding coefficient is 0.43. The microstructure of partial molten zone at A356 alloy side is composed of island Al-Si eutectic and coarse Si particles,and the microstructure of molten zone of weld seam shows typical Al-Si cast eutectic structure. In addition, the microstructure of partial molten zone at 6005 A alloy side contains dendritic and rod shaped Al-Si eutectic and Al(Fe, Mn)Si particles. The mcirohardness of the joint increases with the increase of the distance from the welded center. The hardness of welded zone is the lowest. However, the hardness of the weld zone at6005 A alloy side is higher than that at A356 alloy side.