(1. 南昌航空大學(xué) 航空制造工程學(xué)院，南昌 330063；
2. 哈爾濱工業(yè)大學(xué) 先進(jìn)焊接與連接國家重點(diǎn)實(shí)驗(yàn)室，哈爾濱 150001；
3. 上海航天設(shè)備制造總廠，上海 200245)
摘 要: 采用Nd:YAG脈沖激光器實(shí)現(xiàn)了200 μm厚熱軋態(tài)NiTiNb形狀記憶合金的激光焊接，研究激光平均功率、激光脈寬和激光頻率等主要工藝參數(shù)對焊接接頭形貌的影響，分析了焊縫熱影響區(qū)顯微組織、力學(xué)性能的變化規(guī)律。結(jié)果表明：激光平均功率、激光脈寬和激光頻率需要良好匹配才能獲得較好性能的焊接接頭。當(dāng)激光平均功率為16.8 W、激光脈寬為4.5 ms、激光頻率為4.5 Hz時(shí)，焊縫的抗拉強(qiáng)度最高，達(dá)到母材的95%。隨著激光平均功率、激光脈寬的增加，焊縫熱影響區(qū)的寬度先增加后減小。激光頻率增加后，熱影響區(qū)晶粒變粗。當(dāng)頻率為27 Hz時(shí)，在靠近熱影響區(qū)的焊縫出現(xiàn)了一個(gè)粗大樹枝晶區(qū)域。母材斷口的韌窩大而深，為典型的韌性斷裂。焊縫斷口的韌窩小而淺，呈魚卵形。熱影響區(qū)的顯微硬度高于母材的，低于焊縫中心區(qū)域的。
關(guān)鍵字: NiTiNb形狀記憶合金；激光技術(shù)；激光焊接；工藝參數(shù)；熱影響區(qū)
（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
