【摘要】 大尺寸、复杂结构的ZM6镁合金铸件极易出现裂纹、疏松、气孔和夹杂等铸造缺陷，开发高质量补焊修复技术将有助于推动其更广泛的应用。利用钨极氩弧焊（TIG）补焊技术，针对不同尺寸的圆形坡口，采用优化的焊前预热措施、焊接工艺参数和焊后热处理工艺，对ZM6铸造镁合金TIG补焊焊缝成形、接头组织特征和力学性能进行分析。研究结果表明，针对直径10～40 mm的坡口，采用焊前200℃预热1 h和160 A焊接电流，可以获得无裂纹、无气孔、无未熔合缺陷的补焊接头。补焊接头焊缝区晶粒细化，晶粒尺寸为30～40μm；热影响区宽度较窄，但晶粒发生长大，团簇状析出相明显减少，因此热影响区硬度最低。随着坡口尺寸增大，焊缝区和热影响区的硬度均发生下降，试样拉伸强度降低。拉伸试样主要断裂于热影响区，平均抗拉强度和延伸率达母材的93.7%和95.1%。更多还原

【Abstract】 ZM6 magnesium alloy castings with large size and complex structure are prone to produce defects such as cracks,porosity and inclusions. The development of high-quality welding repair technology will help promote its wider application.In this paper, the argon arc welding technology was used to repair ZM6 cast magnesium alloy with different sizes of circular grooves using optimized pre welding preheating measures, welding process parameters and post welding heat treatment processes. The weld characteristics, microstructure and mechanical properties of argon arc welding repair joints were analyzed.The results showed that for the grooves with diameter of 10～40 mm, the repair welding joint without cracks, pores and incomplete fusion defects was obtained by preheating at 200 ℃ for 1 hour before welding and welding with 160 A current.The grain in the weld area of the repair welding joint was refined, and the grain size was 30～40 μm. The width of the heat affected zone was narrow, but the grains grow and the cluster-like precipitates were significantly reduced. Therefore, the hardness of the heat-affected zone was the lowest. With the increase of groove size, the hardness of weld zone and heat affected zone decreased, and the tensile strength of the sample also decreased. The tensile specimen mainly breaks in the heat affected zone, and the average tensile strength and elongation could reach 93.7% and 95.1% of that of the base metal.更多还原