(1. 南昌航空大学 航空制造工程学院，南昌 330063；
2. 哈尔滨工业大学 先进焊接与连接国家重点实验室，哈尔滨 150001；
3. 上海航天设备制造总厂，上海 200245)
摘 要: 采用Nd:YAG脉冲激光器实现了200 μm厚热轧态NiTiNb形状记忆合金的激光焊接，研究激光平均功率、激光脉宽和激光频率等主要工艺参数对焊接接头形貌的影响，分析了焊缝热影响区显微组织、力学性能的变化规律。结果表明：激光平均功率、激光脉宽和激光频率需要良好匹配才能获得较好性能的焊接接头。当激光平均功率为16.8 W、激光脉宽为4.5 ms、激光频率为4.5 Hz时，焊缝的抗拉强度最高，达到母材的95%。随着激光平均功率、激光脉宽的增加，焊缝热影响区的宽度先增加后减小。激光频率增加后，热影响区晶粒变粗。当频率为27 Hz时，在靠近热影响区的焊缝出现了一个粗大树枝晶区域。母材断口的韧窝大而深，为典型的韧性断裂。焊缝断口的韧窝小而浅，呈鱼卵形。热影响区的显微硬度高于母材的，低于焊缝中心区域的。
关键字: NiTiNb形状记忆合金；激光技术；激光焊接；工艺参数；热影响区
（1.School of Aviation Manufacturing Engineer, Nanchang Aviation University, Nanchang 330063, China;
2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China;
3. Shanghai Spaceflight Manufacture (Group) Co., Ltd., Shanghai 200245, China）
Abstract:Nd:YAG laser was used to weld hot-rolled-state NiTiNb shape memory alloy with thickness of 200 μm. The effects of main process parameters including average power of laser, pulse width of laser and frequency of laser to the morphology of the welding joint were studied, then the transformation law about the microstructure of heat-affected zone and mechanical properties of the welding joint were analyzed. The results indicate that a perfect welding joint needs a good match of average power, pulse width and frequency of laser. The highest tensile strength of welding joint reaches 95% of that of the base material obtained when average power of laser is 16.8 W, pulse width of laser is 4.5 ms and frequency of laser is 4.5 Hz. With increasing the average power and pulse width of laser, the width of heat-affected zone first increases, then decreases. The grains in the heat-affected zone continue to coarsen with increasing the frequency of laser. A gross dendrites area arises in the welding joint near the heat-affected zone when the frequency of laser is 27 Hz. The dimples in the parent material fracture is large and deep, which is classic ductile fracture. The dimples in the welding joint fracture are small and shallow, which look like roes. The micro-hardness of heat-affected zone is higher than that of the base material but lower than that of the centre area of welding joint.
Key words: NiTiNb shape memory alloy; laser technique; laser welding; process parameters; heat affected zone
