(1. 南京航空航天大学 材料科学与技术学院，南京 210016;
2. 中国商飞上海飞机制造有限公司，上海 200436)
摘 要: 借助激光-MIG复合焊技术，采用Invar M93焊丝对厚度为19.05 mm的Invar合金板材进行多层对接焊实验。分析了工艺参数对焊缝熔深、熔宽及深宽比等宏观形貌参数的影响，并研究Invar合金复合焊接头不同区域的显微组织特点及形成原因。结果表明:从打底层到盖面层焊缝的平均深宽比由2.6减小到0.86，热影响区宽度明显增加，焊缝形貌由钉头状转变为高脚杯状。焊缝中心区域形成纵向分布的狭长奥氏体柱状树枝晶，两侧为斜向生长的奥氏体胞状树枝晶。从打底层到盖面层，焊缝中不同区域的晶粒度均逐渐增大。另外，相邻焊缝边界亦存在热影响区，出现联生结晶现象。
关键字: Invar合金;激光-MIG复合焊;焊缝形貌;显微组织;结晶形态
（1. College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;
2. Shanghai Aircraft Manufacturing Co., Ltd., Shanghai 200436, China）
Abstract:Invar alloy plates with thickness of 19.05 mm were welded with Invar M93 filler wire by laser-MIG hybrid welding. The effects of welding parameters on weld appearance including beam penetration, weld witch and depth-to-witch ratio were analyzed. The features and the forming mechanism of the microstructure on different regions of the weld were investigated. The results show that the weld depth-to-witch ratio gradually decreases from 2.6 to 0.86 in average and the witch of HAZ obviously increases from back weld to cover weld, leading to the weld appearance changing from nail-head shape to goblet shape. Narrow Austentic columnar dendrite crystals in longitudinal direction and oblique diagonal cellular dendrite crystal are formed in weld center and off-centered area, respectively. The grain size in different regions of the weld increases layer-by-layer. In addition, HAZ is also found at the boundary of adjacent weld layers, where appears epitaxial solidification.
Key words: Invar alloy; laser-MIG hybrid welding; weld appearance; microstructure; crystal form
