工艺参数对6061-T6铝合金激光焊接接头组织及性能的影响

Influence of Process Parameters on Microstructure and Properties of 6061-T6 Aluminum Alloy Laser Welded Joint

采用激光自熔焊对4 mm厚的6061-T6铝合金板进行对接焊试验。通过金相显微镜、X射线衍射仪、扫描电镜等分析手段对焊接接头的宏观形貌和微观组织进行观察。利用显微硬度计和万能拉伸试验机对焊接接头进行力学性能检测。结果显示:激光焊接参数对6061-T6铝合金焊缝宏观形貌有显著影响。采用适当的激光焊接参数能得到成型良好的焊缝和较低的气孔率。最优的焊接参数为激光功率4.8 kW,焊接速度30 mm/s,离焦量-1 mm。熔合线附近组织为垂直于熔合线方向生长的柱状晶,焊缝中心组织由细小的树枝晶组成,晶粒尺寸明显低于母材的。6061-T6铝合金激光焊接头的显微硬度曲线接近于“U”形,其中,焊缝中心硬度较低,约为65 HV。接头试样断裂位置均处于焊缝区,焊接接头的抗拉强度最高可达到母材的71.7%,断裂类型属于准解理断裂。

The butt-welding tests of 4 mm thick 6061-T6 aluminum alloy plate were carried out by using laser self-fusion welding.Metallographic microscope,X-ray diffractometer and scanning electron microscope were used to analyze the macro-morphology and microstructure of the welded joints.The mechanical properties of the welded joints were tested by microhardness tester and universal tensile testing machine.The results show that the laser welding parameters have a significant effect on the macro-morphology of 6061-T6 aluminum alloy welded joints.The weld with good formation and low porosity can be obtained by using appropriate laser parameters.The optimized welding parameters are laser power of 4.8k W,welding speed of 30mm/s,defocusing amount of-1 mm.The microstructure near the fusion line is columnar crystal growing perpendicular to the fusion line,the weld center is composed of fine dendrites,and the grain size is obviously smaller than that of the base metal.The microhardness curve of 6061-T6 aluminum alloy laser welding joints is close to"U"shape,and the microhardness of the weld center is the lowest,about 65HV.The fracture positions of the joint specimens are in the weld zone,and the maximum tensile strength of the welded joint reaches 71.7%of the base metal.The fracture type belongs to quasi cleavage fracture.