(華中科技大學(xué) 光電科學(xué)與工程學(xué)院，武漢 430074)
摘 要: 采用高功率CO2激光器對(duì)MB8鎂合金進(jìn)行一系列激光焊接工藝試驗(yàn)，并對(duì)焊縫成形的形成規(guī)律、接頭的微觀組織和力學(xué)性能進(jìn)行研究。結(jié)果表明：焊縫熔深基本和激光功率呈正比關(guān)系，激光功率每增加1 kW，熔深約增加2 mm。焊縫熔合區(qū)組織主要由粗大的等軸晶組成，晶粒內(nèi)有連續(xù)析出的條紋狀β-Mn，晶粒尺寸約為60 μm；熱影響區(qū)組織為相對(duì)細(xì)小但大小不一的等軸晶，晶粒尺寸為15~40 μm。在消除焊縫表面缺陷后，焊接接頭抗拉強(qiáng)度能達(dá)到基材的90 %左右。此外，熔合區(qū)內(nèi)的粗大晶粒、晶粒內(nèi)連續(xù)分布的第二相及焊縫內(nèi)氣孔缺陷是造成接頭拉伸性能低于基材的主要原因。
關(guān)鍵字: MB8鎂合金；激光焊接；焊縫成形；微觀組織；力學(xué)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
