超薄NiTiNb记忆合金激光焊焊缝成形及热影响区的组织和性能
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摘要
采用Nd:YAG脉冲激光器实现了200μm厚热轧态Ni Ti Nb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27Hz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。
Nd:YAG laser was used to weld hot-rolled-state Ni Ti Nb 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.
Nd:YAG laser was used to weld hot-rolled-state Ni Ti Nb 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.
引文
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[15]颜莹,金伟,周亭俊.热轧Ni47Ti44Nb9形状记忆合金板材的织构及其对拉伸和恢复性能的影响[J].中国有色金属学报,2010,20(11):2148-2153.YAN Ying,JIN Wei,ZHOU Ting-jun.Texture and its influence on tensile and recoverable properties of hot-rolled Ni47Ti44Nb9shape memory alloy sheet[J].The Chinese Journal of Nonferrous Metals,2010,20(11):2148-2153.
[2]HE X M,RONG L J,YAN D S,LI Y Y.Ti Ni Nb wide hysteresis shape memory alloy with low niobium content[J].Materials Science and Engineering A,2004,371(1):193-197.
[3]CHAN C W,CHAN S H J,MAN H C,JI P.Constitutive model for localized Lüders-like stress-induced martensitic transformation and super-elastic behaviors of laser-welded Ni Ti wires[J].Computational Materials Science,2012,63:197-206.
[4]SUGAWARA T,HIROTA K,WATANABE M,MINETA T,MAKINO E,TOH S,SHIBATA T.Shape memory thin film actuator for holding a fine blood vessel[J].Sensors and Actuators A:Physical,2006(130):461-467.
[5]BANSIDDHI A,DUNAND D C.Shape-memory Ni Ti-Nb foams[J].J Mater Res,2009,24(6):2107-2117.
[6]吴冶,孟祥龙,蔡伟,赵连城.Ni_(47)Ti_(44)Nb_9合金丝氩弧焊接头的显微组织和力学行为[J].材料科学与工艺,2005,13(3):312-315.WU Ye,MENG Xiang-long,CAI Wei,ZHAO Lian-cheng.Microstructure and mechanical behaviors of Ti Ni Nb wide hysteresis shape memory alloy wire argon arc welding joint[J].Materials Science and Technology,2005,13(3):312-315.
[7]韩立军,赵熹华,赵蕾,张甫.Ti Ni Nb形状记忆合金丝精密脉冲电阻对焊工艺分析[J].材料科学与工艺,1999,7(3):76-79.HAN Li-jun,ZHAO Xi-hua,ZHAO Lei,ZHANG Fu.Analysis of welding parameters of precise pulse resistance butt welding on Ti Ni Nb shape memory alloys[J].Materials Science and Technology,1999,7(3):76-79.
[8]GRUMMON D S,LOW K B,FOLTZ J,SHIBATA T,SHAW J A.A New method for brazing nitinol based on the quasi-binary Ti Ni-Nb system[C].48th AA/ASME/ASCE/AHS/ASC Structures,Structural Dynamics,and Materials Con.2007
[9]CHAN C W,MAN H C.Laser welding of thin foil nickel-titanium shape memory alloy[J].Optics and Lasers in Engineering,2011,49(1):121-126.
[10]GONG W H,CHEN Y H,KE L M.Microstructure and properties of laser micro welded joint of Ti Ni shape memory alloy[J].Transactions of Nonferrous Metals Society of China,2011,21(9):2044-2048.
[11]FALVO A,FURGIUELE F M,MALETTA C.Laser welding of a Ni Ti alloy:Mechanical and shape memory behaviour[J].Materials Science and Engineering A,2005,412(1):235-240.
[12]BRAZ FEMANDES F M,MAHESH K K,CRACIUNESCU C M,OLIVEIRA J P,SCHELL N,MIRANDA R M,QUINTINO L,AUINTINO L,OCANA J L.In Situ Structural Characterization of Laser Welded Ni Ti Shape Memory Alloys[C]//Materials Science Forum,2013,738:338-343.
[13]VIEIRA L A,FERNANDES F M,MIRANDA R M,SILVA R J C,QUINTINO L,CUESTA A,OCANA J L.Mechanical behaviour of Nd:YAG laser welded super elastic Ni Ti[J].Materials Science and Engineering A,2011,528(16):5560-5565.
[14]莫华强,李聪,王丛林,邱少宇,祖小涛,沈保罗,封向东,黄德诚.Ni Ti Nb形状记忆合金的组织研究[J].核动力工程,2004,24(6):559-562.MO Hua-qiang,LI Cong,WANG Cong-lin,QIU Shao-yu,ZU Xiao-tao,SHEN Bao-luo,FENG Xiang-dong,HUANG De-cheng.Structural study of a Ni Ti Nb shape memory alloy[J].Nuclear Power Engineering,2004,24(6):559-562.
[15]颜莹,金伟,周亭俊.热轧Ni47Ti44Nb9形状记忆合金板材的织构及其对拉伸和恢复性能的影响[J].中国有色金属学报,2010,20(11):2148-2153.YAN Ying,JIN Wei,ZHOU Ting-jun.Texture and its influence on tensile and recoverable properties of hot-rolled Ni47Ti44Nb9shape memory alloy sheet[J].The Chinese Journal of Nonferrous Metals,2010,20(11):2148-2153.