(华中科技大学 光电科学与工程学院，武汉 430074)
摘 要: 采用高功率CO2激光器对MB8镁合金进行一系列激光焊接工艺试验，并对焊缝成形的形成规律、接头的微观组织和力学性能进行研究。结果表明：焊缝熔深基本和激光功率呈正比关系，激光功率每增加1 kW，熔深约增加2 mm。焊缝熔合区组织主要由粗大的等轴晶组成，晶粒内有连续析出的条纹状β-Mn，晶粒尺寸约为60 μm；热影响区组织为相对细小但大小不一的等轴晶，晶粒尺寸为15~40 μm。在消除焊缝表面缺陷后，焊接接头抗拉强度能达到基材的90 %左右。此外，熔合区内的粗大晶粒、晶粒内连续分布的第二相及焊缝内气孔缺陷是造成接头拉伸性能低于基材的主要原因。
关键字: MB8镁合金；激光焊接；焊缝成形；微观组织；力学性能
CO2 laser welding of MB8 magnesium alloy
（School of Optoelectronics Science and Engineering,
Huazhong University of Science and Technology, Wuhan 430074, China）
Abstract:A series of experiments on high power CO2 laser welding of MB8 magnesium alloy were carried out, and the forming rules of the weld seams, the microstructures and tensile strengths of the welded joints were also studied. The results show that the weld penetration depth is in the direct proportion to the laser power, when the laser power is increased by 1 kW, the penetration depth will be increased by about 2 mm. The microstructure of fusion zone center is mainly composed of coarse equiaxed grain with the size of about 60 μm and the precipitating stripe β-Mn is observed in the grains. The microstructures of heat affected zone are of equiaxed grains with different sizes from 15 to 40 μm. The tensile strength of the laser welded MB8 magnesium alloy reaches up to about 90% of that of the substrate after the surface defects are avoided. Moreover, the coarse grain of fusion zone, continuous second phase (β-Mn) and weld porosity are the main factors that result in lower tensile strength of laser welds in comparison of substrate.
Key words: MB8 magnesium alloy; laser welding; weld shape; microstructure; mechanical properties
