Mg-Al-Zn合金激光填丝焊接接头的显微组织与力学性能

Microstructure and Mechanical Property of Mg-Al-Zn Alloy Joint by Laser Beam Welding with Filler Wire

采用激光填丝焊方法对4 mm厚的Mg-Al-Zn系镁合金进行焊接,采用金相显微镜、扫描电镜、透射电镜和X射线衍射仪对接头的微观组织进行分析,并对接头的拉伸性能和显微硬度进行测试。结果表明,接头焊缝区主要由α-Mg基体相和β-Mg17Al_(12)强化相组成。与母材区相比,接头热影响区的硬度有所降低,与该区域的晶粒粗化有关。在激光功率3.0 kW,焊接速度1.5 m/min,送丝速度2.1 m/min的工艺条件下获得的接头,焊缝成形良好,其抗拉强度为315 MPa,与母材的抗拉强度接近。接头拉伸断口上分布着一定数量的韧窝和河流花样,总体呈韧-脆混合型断裂特征。

Mg-Al-Zn magnesium alloy with the thickness of 4 mm was welded by using laser beam welding with filler wire.The microstructure of the welded joints was analyzed by using optical microscope,scanning electron microscope,transmission electron microscope and X-ray diffractometer,and the tensile property and microhardness of the welded joints were tested.The results show that the weld zone is mainly composed of matrix phaseα-Mg and strengthening phaseβ-Mg17Al_(12).Compared with that of the base metal,the hardness of the heat-affected zone decreases in a certain extent,which is related to the coarse grains in this region.Under the welding parameters of laser power of 3.0 kW,welding speed of 1.5 m/min and wire feeding rate of 2.1 m/min,the welded joint with good appearance is obtained.The tensile strength of the welded joint is 315 MPa,which is close to that of the base metal.Some dimples and river pattern are distributed on the tensile fracture of the joint,and it is overall characterized by the mixed mode of ductile-brittle fracture.