(1. 南昌航空大学 轻合金加工科学与技术国防重点学科实验室，南昌 330063；
2. 上海航天设备制造总厂，上海 200245)
摘 要: 为实现0.2 mm厚度TiNiNb形状记忆合金的良好焊接，采用低功率脉冲激光对其进行对接焊试验，研究激光功率对焊缝表面成形、焊接接头横截面形貌和抗拉强度的影响规律以及焊接接头的微观组织结构。结果表明：当激光功率不低于16.8 W时能实现焊透，且焊缝熔宽随着激光功率的增大而增加，但随着激光功率的增大，焊缝表面飞溅比较严重。当激光功率为15.1 W时，焊缝未焊透、焊接接头抗拉强度较低；当激光功率增大到16.8 W以上时，随着激光功率的增大，接头抗拉强度呈现略微减小的趋势。焊接接头中焊缝中心为细小等轴晶，熔池边缘为柱状晶。焊缝上边缘基本不存在热影响区，在焊接接头底部存在约10 μm宽度的热影响区。
关键字: TiNiNb形状记忆合金；激光微焊接；焊缝成形；显微组织；性能；激光功率
（1. National Defense Key Disciplines Laboratory of Light Alloy Processing Science and Technology,
Nanchang Hangkong University, Nanchang 330063, China;
2. Shanghai Spaceflight Manufacture (Group) Co., Ltd., Shanghai 200245, China）
Abstract:In order to achieve good welding of 0.2 mm-thick TiNiNb shape memory alloy (SMA) sheet, butt welding was carried out using low power impulse laser. Influences of laser power on the weld formation, cross section morphology, tensile strength and microstructure of the welded joint were studied. The results show that when the laser power is no less than 16.8 W, full penetration welded joint can be got. Weld width increases with the increase of laser power but the welding spatter is serious. When the laser power is 15.1 W, lack of penetration decreases the tensile strength of the welded joint. The tensile strength slightly decreases with the increasing of the laser power when the laser power is greater than 16.8 W. The microstructure of the weld joint consists of fine equiaxed grains in the weld center and columnar crystals on the edge of molten pool. There is almost no heat-affected zone (HAZ) on the weld edge, but there is HAZ with about 10 μm width on the bottom of the welded joint.
Key words: TiNiNb shape memory alloy; micro laser welding; weld formation; microstructure; properties; laser power
