2219-T87铝合金拉锻式摩擦塞补焊接头组织及性能杜 波1， 杨新岐1， 孙转平1,2， 王东坡1(1. 天津大学 天津市现代连接技术重点实验室，天津 300350；2. 天津长征火箭制造有限公司，天津 300451)摘 要： 对6 mm 厚的2219-T87铝合金板进行了拉锻式摩擦塞补焊试验，对焊接接头的微观组织、显微硬度、抗拉强度及拉伸断口进行了观察与测试. 结果表明，采用优化的摩擦塞补焊工艺可实现2219-T87铝合金母材和2219-T87铝合金塞棒的冶金连接. 拉锻式摩擦塞补焊过程中，塞棒承受拉应力，应优化接头设计和焊接工艺参数从而防止塞棒被拉断. 未焊合是接头的主要缺陷，易出现在接头的近上表面处. 焊缝区发生明显软化，最低硬度出现在靠近连接界面的塞棒热力影响区，最低值为84.4 HV . 接头的抗拉强度可达326.4 MPa ，断后伸长率可达4.45%，抗拉强度和断后伸长率分别为母材的71.7%和44.5%，拉伸断口呈韧窝形貌.关键词： 拉锻式摩擦塞补焊；2219-T87铝合金；工艺特征；微观组织；力学性能中图分类号：TG 453.9 文献标识码：A doi ：10.12073/j .hjxb .20194000550 序 言摩擦塞补焊(friction plug welding ，简称FPW)是英国焊接研究所于1995年发明的一种新型固相补焊技术[1]，该技术主要用于搅拌摩擦焊尾孔的消除及其它焊接缺陷的修复，在火箭贮箱结构的制造过程中具有重要应用. 相对于FPW 工艺，拉锻式摩擦塞补焊(friction pull plug welding ，简称FPPW)的焊机和支撑垫板位于被焊件的同一侧，对于背部无法安装支撑垫板、结构复杂、体积庞大的构件，FPPW 可有效避免垫板位置的限制，且焊接设备简单，操作容易，具有明显的优势. 洛克希德—马丁公司、马歇尔飞行中心以及英国焊接研究所对FPPW 进行了大量的研究工作[2]. Metz 等人[3-4]研究了2195铝锂合金FPPW 接头的组织特征及疲劳特性. 国内对摩擦塞补焊的研究主要集中在FPW 接头的组织与性能方面[5-9]，与FPPW 相关的研究很少[10-12]，尚未见到有关2219-T87铝合金FPPW 技术的报道.文中采用火箭贮箱结构用6 mm 厚2219-T87铝合金板材和2219-T87塞棒进行了FPPW 工艺试验，成功实现了FPPW 工艺过程并获得了无宏观缺陷的焊缝组织，同时对FPPW 接头的微观组织、显微硬度、抗拉强度、拉伸断口进行了观察和测试.研究结果将为FPPW 技术应用于火箭贮箱结构的制造提供重要试验依据.1 试验方法母材和塞棒材料均采用2219-T87铝合金，文中所用试验板规格为200 mm × 80 mm × 6 mm ，母材的抗拉强度为455 MPa ，断后伸长率为10%.2219-T87铝合金的主要化学成分见表1.表 1 2219-T87铝合金的主要化学成分(质量分数，%)Table 1 Chemical composition of 2219-T87 aluminumalloyCu Mn Fe Si Zn Mg Zr Ti5.8 ~6.80.2 ~ 0.40. 30.20.10.020.1 ~ 0.250.02 ~ 0.1FPPW 工艺试验在天津大学自主设计研制的拉锻式摩擦塞补焊试验机上完成，设备示意图如图1示. 塞棒和塞孔的形状尺寸如图2a ，2b 所示. 通过初步工艺试验，选取优化的工艺参数进行试验(表2)，塞棒压入量选为5 mm .焊缝截面经磨光、抛光后用Keller 试剂腐蚀并在OLYMPUS GX51光学显微镜下观察其显微组织.使用432SVD 自动转塔数显维式硬度计测量接头的硬度分布，载荷10 N ，加载时间10 s . 依据国家标准GB/T 2651—2008《焊接接头拉伸试验方法》进行焊接接头拉伸试验，拉伸试样尺寸如图2c收稿日期：2017 − 12 − 18基金项目：天津市应用基础与前沿技术研究计划(C02015062)第 40 卷 第 2 期2019 年 2 月焊 接 学 报TRANSACTIONS OF THE CHINA WELDING INSTITUTIONVol .40(2):128 − 132February 2019所示，拉伸测试在CSS-44100 电子万能试验机上进行，加载速率3 mm/min . 使用Hitachi-S4800扫描电镜观察拉伸断口的宏观与微观形貌.支撑机构待焊工件塞棒焊机主轴图 1 FPPW 设备示意图Fig. 1 Illustration of FPPW equipment55°2818649418555°2828M25M2555°f 322523R 15R 4R 25(a) 接头设计 A (b) 接头设计 B (c) 拉伸试样尺寸FPPW 焊接f 32图 2 接头设计及拉伸试样尺寸(mm)Fig. 2 Joint design and dimensions of tensile specimen表 2 试样编号及焊接工艺参数Table 2 Specimen codes and welding parameters编号转速n /(r·min −1)焊接压力F n /kN 顶锻压力F d /kN 保压时间t /s A 7 00025305B7 000253052 试验结果与分析2.1焊接工艺及成型特征图3a 为接头设计和工艺参数不合理时塞棒被拉断的FPPW 接头外观，图3b 为成形良好的FPPW 接头的外观. 与FPW 工艺不同，FPPW 过程中塞棒承受拉应力，塞棒容易被拉断，塞棒被拉断会严重影响焊缝成形和连接质量，因此应该避免塞棒被拉断. 这就要求塞棒直径应该足够大以承受焊接拉应力，如果塞棒直径过小则很容易在焊接过程中被拉断，但塞棒过粗又会增加热输入从而加剧接头的软化和变形. 此外还应该避免塞棒与支撑垫板孔的侧壁发生摩擦，如果二者发生摩擦，塞棒会因受热强度降低而被拉断.(a) 塞棒被拉断(b) 成形良好图 3 FPPW 接头外观Fig. 3 Appearance of FPPW joints塞棒承受焊接拉应力这一特点也对FPPW 的焊接工艺参数提出了新的要求. 在保证焊接质量的前提下，应尽可能的降低焊接压力和焊接转速，从而降低焊接热输入，焊接压力的降低还可以在一定程度上减小塞棒直径. 此外，塞棒进给量也应严格控制，在保证塞孔充分填充的情况下不宜过大，避免进给量过大导致塞棒与支撑板孔的侧壁摩擦.FPPW 的工艺特点使得接头设计和工艺参数的优化尤为重要.图4a ，4b 分别为接头A 和接头B 焊缝截面的宏观形貌. 由图4可以看出，接头不同区域的组织差异较为明显，接头整体形状与塞棒形状相近. 根据FPPW 接头的组织特征，可将接头分为塞棒区(PM ，plug metal)、塞棒热力影响区(PTMAZ ，plug thermo-mechanically affected zone)、再结晶区(RZ ，recrystallized zone)、热力影响区(TMAZ ，thermo- mech-anically affected zone)、热影响区(HAZ ，heat affected zone)和母材区(BM ，base metal)六个部分.ABC D E F(a) 接头 A(b) 接头 B图 4 FPPW 接头的宏观形貌Fig. 4 Macro graphs of FPPW joints图5a ，5b 为图4a 中所示缺陷的微观特征，FPPW 接头的缺陷多出现在接头的近上表面处. 焊接过程中由于塞棒压入，材料软化导致塞孔上部变形，同第 2 期杜 波，等：2219-T87铝合金拉锻式摩擦塞补焊接头组织及性能129时母材上表面处的塑性材料翻卷形成飞边，翻卷的塑性材料与塞棒之间没有外力约束，呈自由状态，很容易形成在接头上部形成未焊合缺陷. 而塞棒B采用的设计则能对上表面翻卷的飞边形成约束，保证塑性材料与塞棒之间紧密接触，可有效避免未焊合缺陷.(a) 区域 A 200 μm(b) 区域 B200 μm图 5 FPPW接头缺陷Fig. 5 Defects of FPPW joint2.2 微观组织特征图6为图4b中所标注位置的微观组织特征，2219-T87铝合金是经过固溶处理 +7%冷加工变形，然后人工时效获得，母材为板条状的轧制组织. FPPW 过程中，发生了剧烈的热力耦合作用，接头各区域的组织发生了显著地改变.50 μm(a) 区域 C50 μm(b) 区域 D100 μm (c) 区域 E100 μm (d) 区域 F图 6 FPPW接头的微观组织形貌Fig. 6 Microstructures of FPPW joint塞棒与塞孔侧壁接触界面处发生的热力作用最为剧烈，材料迅速软化并发生剧烈的塑性流动，再结晶形成晶粒均匀细小的等轴晶区. 接头的下表面位置最先与塞孔接触，经历焊接热循环的时间也最长，所形成的RZ的宽度较上表面处大，晶粒尺寸也较大(图6a，6b). 靠近摩擦界面处的TMAZ组织发生了部分再结晶(图6a，6b)，远离连接界面的TMAZ 在热力作用下发生了明显的塑性变形，晶粒的形态130焊 接 学 报第 40 卷在接头的不同位置也明显不同(图6c ，6d ).2.3 硬度分布图7为接头B 截面中心厚度处的硬度分布，硬度测试间距为1 mm . 实测2219-T87铝合金板的平均硬度为146.5 HV ，2219-T87铝合金棒材平均硬度为141 HV .14012010080−30−20−100距塞棒中心的距离 D /mm102030硬度 H (H V )图 7 FPPW 接头硬度分布Fig. 7 Hardness distribution of FPPW jointFPPW 接头的硬度从HAZ 开始降低，在连接界面两侧的TMAZ 和PTMAZ 达到最低，最低值为84.4 HV ，为母材硬度的57.6%. 塞棒区由于摩擦热传导作用，也出现了明显的软化，硬度在85 ~90 HV 范围内波动，总体上略高于TMAZ . 此外，由于FPPW 的塞棒较粗，焊接过程中产生的摩擦热也比较多，使得接头HAZ 的宽度明显比FPW 接头大.在FPPW 过程中，发生了剧烈的热力耦合作用，造成塞补焊缝区域软化，接头的软化主要有两方面原因. 一是焊接热循环使母材的冷加工变形强化作用消失. 二是基体主要的强化相θ′相发生溶解，部分θ′相相聚集长大形成θ相，材料出现了过时效，导致硬度下降，强度降低.2.4 拉伸性能图8为FPPW 接头、FPW 接头以及2219-T87母材的抗拉强度及断后伸长率柱状图. FPPW 接头的抗拉强度可达326.4 MPa ，断后伸长率为4.45%，分别为母材的71.7%和44.5%，与FPW 的强度相当[8-9]. 拉伸试验中，试样的断裂位置在连接界面附近，断口呈圆弧状，说明连接界面及附近的软化区是整个焊缝的薄弱区域.400300200100抗拉强度 R m /M P a断后伸长率 A (%)抗拉强度断后伸长率母材FPW FPPW1412108642图 8 FPPW 接头抗拉强度及断后伸长率Fig. 8 Tensile strength and elongation of FPPW joint2.5 断口形貌图9为FPPW 接头拉伸试样的断口形貌. 拉伸试样的断裂位置为连接界面、连接界面附近软化的TMAZ 和PTMAZ . 由断口形貌可以看出，FPPW 接头的拉伸断口呈现两种韧窝形貌. 断裂位置在TMAZ 和PTMAZ 的韧窝平而浅，且尺寸较大，韧窝底部分布有大尺寸的第二相，说明焊接过程中TMAZ 和PTMAZ 中的第二相聚集长大(图9a ). 断裂位置在连接界面的韧窝呈等轴状，尺寸较小，分布均匀，说明焊接过程中连接界面处发生了再结晶(图9b ).20 μm(b) 断裂在 RZ20 μm (a) 断裂在 TMAZ图 9 FPPW 接头拉伸断口形貌Fig. 9 Tensile fracture morphology of FPPW joint3 结 论(1) 通过优化接头设计和工艺参数，实现6 mm厚2219-T87铝合金板材和2219-T87铝合金塞棒的FPPW 工艺过程，获得了无宏观缺陷的焊缝组织.(2) 在FPPW 过程中，塞棒承受拉应力，接头设第 2 期杜 波，等：2219-T87铝合金拉锻式摩擦塞补焊接头组织及性能131计和焊接工艺参数不合理时塞棒会被拉断，从而影响接头的连接质量和焊接过程的稳定性. 应通过对FPPW 过程的接头设计和焊接工艺参数进行优化，避免塞棒被拉断.(3) FPPW 接头的典型缺陷为未焊合，易出现在接头的近上表面处，主要是由于塞棒与上表面软化的飞边之间缺少力的约束所致. 采用接头设计B 可有效避免未焊合缺陷的形成.(4) FPPW 接头的焊缝组织发生软化，最低硬度出现在连接界面附近的PTMAZ ，最低值为84.4 HV .接头抗拉强度可达326.4 MPa ，断后伸长率最高为4.45%，分别为母材的71.7%和44.5%.参考文献：Riki Takeshita, Terry L, Kenner. Friction plug welding UnitedStates US: 6213379BI[P]. 2001−4−10[1]Richard F. Bringing aerospace welding specifications up to stand-ard[J]. Welding and Metal Fabrication, 2000, 68(7): 12 − 14.[2]Metz D F, Barkey M E. Fatigue behavior of friction plug welds in2195 Al–Li alloy[J]. International Journal of Fatigue, 2012, 43(1):178 − 187.[3]Metz D F, Weishaupt E R, Barkey M E, et al . A microstructureand microhardness characterization of a friction plug weld in fric-tion stir welded 2195 Al-Li[J]. Journal of Engineering Materials & Technology, 2012, 134(2): 1 − 7.[4]栾国红, 季亚娟, 董春林, 等. LY12铝合金摩擦塞补焊接头组织分析[J]. 焊接学报, 2006, 27(10): 1 − 3.Luan Guohong, Ji Yajuan, Dong Chunlin, et al . Microstructure of LY12 aluminium alloy welded joint of friction plug welding[J].Transactions of the China Welding Institution, 2006, 27(10): 1 − 3.[5]陈忠海, 陈家庆, 焦向东, 等. 2024铝合金圆柱形组合的FHPP 试验分析[J]. 焊接学报, 2009, 30(11): 1 − 3.Chen Zhonghai, Chen Jiaqing, Jiao Xiangdong, et al . 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Materials Science & Engineering A, 2017, 693: 129 −135.[9]赵衍华, 刘景铎, 张加涛, 等. 2014铝合金拉锻式摩擦塞补焊接头微观组织及力学性能[J]. 航空制造技术, 2009(23): 86 − 90.Zhao Yanhua, Liu Jingduo, Zhang Jiatao, et al . Microstructure and mechanical property of friction plug welding joint of 2014 Al alloy[J]. Aeronautical Manufacturing Technology, 2009(23): 86 −90.[10]赵衍华, 刘景铎, 张丽娜, 等. 2014铝合金搅拌摩擦焊缝的拉锻式摩擦塞补焊[J]. 航空材料学报, 2010, 30(1): 41 − 46.Zhao Yanhua, Liu Jingduo, Zhang Lina, et al . Study on Friction Plug Welding of 2014 Aluminum Alloy FSW Joint[J]. Journal of Aeronautical Materials, 2010, 30(1): 41 − 46.[11]王国庆, 赵衍华, 孔德跃, 等. LD10铝合金熔焊接头缺陷的拉锻式摩擦塞补焊[J]. 焊接, 2010(6): 38 − 42.Wang Guoqing, Zhao Yanhua, Kong Deyue, et al . Friction pull plug welding of LDl0 aluminum alloy defects in TIG joints[J].Welding & Joining, 2010(6): 38 − 42.[12]第一作者简介：杜 波，男，1990年出生，博士研究生. 研究方向为摩擦塞补焊. Email: dubo1122@tju .edu .cn通信作者简介：杨新岐，男，博士，教授. Email: xqyang@tju .edu .cn132焊 接 学 报第 40 卷proposed algorithm can effectively realize the real-time tracking of the solid-liquid separation point of the molten pool tail in GTAW-based additive manufacturing. The algorithm is simple, efficient and has a good anti-interference ability.Key words: GTAW-based additive manufacturing；molten pool tail；solid-liquid separation point；real-time detec-tionEffects of C-MoS2-Fe2O3(Fe3O4) nano-lubricants on contact tip wear for non-copper coated solid wires WAN Qian1，LI Zhuoxin1， ZHANG Tianli2， KIM Hee Jin3 (1. College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124, China；2. School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China；3. Advanced Joining Research Team, Korea Institute of Industrial Technology, Cheonan-si 330-825, Korea). pp 110-115Abstract: Aiming at the application of contact tip wear of non-copper coated solid wires in robot auto-welding, C-MoS2-Fe2O3(Fe3O4) nano-composite lubricants were prepared on the surfaces of non-copper coated solid wires by a mechanical coating technique. The effects of C-MoS2-Fe2O3(Fe3O4) lubricants proportion on the contact tip wear were investigated. The results demonstrate that lubricating property of C-Fe3O4coatings outperformed lubricating property of C-Fe2O3coatings. The anti-wear performance of the contact tip was enhanced with an addition of nano-MoS2. The formation of protective self-repairing films at the rubbing interface of welding wires against the contact tip was attributed to the tribochemical reaction among lubricants. The tribofilm composition were FeO, MoS2and MoO3which lubricating properties are excellent. They can avoid direct contact of welding wires against the contact tip, thus the contact tip wear was inereasdel. Oxidative wear, abrasive wear and arc ablation were the primary mechanisms of the contact tip wear.Key words: non-copper coated solid wire；nano-com-posite lubricant；contact tip wear；friction self-repairingOptimal design of reliability and signal integrity for embedded micro-scale BGA solder joint LU Liangkun1，HUANG Chunyue1， HUANG Genxin1， LIANG Ying2， LI Tianming3 (1. School of Electro-Mechanical Engineering, Guilin University of Electronic Technology, Guilin 541004, China；2. Department of Electronic Engineering, Chengdu Aeronautic Vocational and Technical College, Chengdu 610021, China；3. Department of Automobile and Power Engineering, Guilin University of Aerospace Technology, Guilin 541004, China). pp 116-122Abstract: A finite element analysis model of ball grid array(BGA) solder joints and a three-dimensional electromagnetic simulation model were established, respectively. The radial dimension, the height and the pad diameter of the solder joint were selected as design variables. The thermal fatigue life and the return loss of the solder joint were selected as the target. The multi-objective optimization design of BGA solder joints was carried out by the combination of experiments and grey correlation analysis. The signal integrity optimization results were verified by experiment. The results show that: after optimization the maximum equivalent stress of solder joints was decreased by 8.2%. The return loss decreased by 11.8% and fatigue life increased 2.15 times. The signal integrity experiment verified the effectiveness of the optimization results.Key words: BGA solder joint；orthogonal experiment；grey relational analysis；reliability；signal integrityMechanism and mechanical property of Si-glass-Si anodic bonding process CHEN Daming1， HU Lifang1,2， SHI Fangrong1， MENG Qinsen1 (1. Department of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China；2. Shanxi Key Laboratory of Advanced Magnesium-based Materials, Taiyuan University of Technology, Taiyuan 030024, China). pp 123-127Abstract:Si-glass-Si was successfully bonded together through a two-step anodic bonding process. The bonding current in each step of the two-step bonding process was investigated, and found to be quite different. The first bonding current decreased quickly to a relatively small value. But for the second bonding step, there were two current peaks, the current varified as decrease-increase-decreased rule. SEM was conducted to investigate the interfacial structure of the Si-glass-Si samples. Tensile tests indicated that the fracture occurred at the glass substrate and bonding strength increased with the increment of the bonding voltage.Key words: anodic bonding；Si-glass-Si；electronic packaging；bonding strengthMicrostructures and properties of 2219-T87 aluminum alloy friction pull plug welds DU Bo1， YANG Xinqi1，SUN Zhuanping1,2， WANG Dongpo1 (1. Tianjin Key Laboratory of Advanced Joining Technology, Tianjin University, Tianjin 300350, China；2. Tianjin Changzheng Rocket Manufacturing Co., Ltd., Tianjin 300451, China). pp 128-132Abstract:Friction pull plug welding (FPPW) experiments were performed for 6mm thick 2219-T87 aluminum alloy. The microstructures, microhardness, tensile strength and tensile fracture surface of FPPW joints were observed and tested respectively. It is verified that metallurgical combination was realized between 2219-T87 plate and 2219-T87 plug using optimized FPPW process. In FPPW process, plug was subjected to tensile stress. Joint design and welding parameters are optimized to prevent plug from being broken off. Lack of bonding was the main defect for FPPW joint, which was easily formed near the upper surface. Softening was observed in the weld zone, the minimum hardness (84.4 HV) appeared in plug thermo-mechanical affected zone. The tensile strength and elongation of FPPW joint can reach to 326.4 MPa and 4.45%, which are equivalent to 71.7% and 44.5% of the base metal. The tensile fracture morphologies are characterized by dimples.VI TRANSACTIONS OF THE CHINA WELDING INSTITUTION2019, Vol. 40, No. 2Key words: friction pull plug welding；2219-T87 alu-minum alloy；process characteristic；microstructure；mechanic-al propertyComparative analysis on mechanical properties of dissimilar steel welded joints by LMHW and MIG welding ZHOU Shujun1， WU Youfa1， YANG Yi1， LIU Xu2，ZHAN Xiaohong1 (1. College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China；2. Yangzhou Dongsheng Automotive Co., Ltd., Yangzhou 211400, China). pp 133-137Abstract: Laser-MIG hybrid welding (LMHW), which combines the advantages of both laser and arc independent heat sources as well as greatly avoids their disadvantages, is a new welding method with great application prospects in the fields of automobiles, ships, petrochemicals, etc. The differences in microstructure and hardness distribution of the dissimilar steel welded joints of 25CrMo4 and 33MnCrB5-2 by LMHW and MIG welding were investigated. The results show that the effect of LMHW was better than that of MIG welding, performing an uniform and full weld seam. LMHW joints exhibited higher overall hardness, finer microsfructure in welding joint centre and better joint quality than MIG welding joints. Specifically, the overall hardness of welded joints of LMHW was 30% higher than MIG welding.Key words: LMHW；MIG welding；laser remelting；mechanical properties；microstructureNumerical simulation of welding residual stress and distortion in Q345/316L dissimilar steel HUANG Bensheng1， CHEN Quan1， YANG Jiang1， LIU Ge2， YI Hongyu1 (1. School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China；2. School of Mechanical and Electrical Engineering, Yangtze Normal University, Chongqing 408100, China). pp 138-144 Abstract: Based on SYSWELD finite element analysis software, the transient temperature distribution, residual stress and deformation of Q345/316L dissimilar steels were nume-rically simulated, and the simulation results were validated by the experimental method. The experimental results show a good agreement with the numerical simulation results, which proved the reliability of the dissimilar steel welding of SYSW-ELD simulation. The results show that the welding tempera-ture field of dissimilar steel was asymmetric, and the Q345 side had a wider range of high temperature regions. Both the transverse and longitudinal residual stresses were in the shape of cap in the direction of the weld and there was a maximum residual stress in the middle of the weld. In the middle of perpendicular welding cross section, the longitudinal residual stress and transverse residual stress were not continuous weld and weld near the central section of the weld. There was a large stress gradient and the stress state was complex. The maximum residual stress appeared in Q345 side of the fusion line. The simulation results under different heat input show that, under the premise of ensuring the quality of welded joints, it was best to use a small heat in welding process.Key words: dissimilar steel welding；numerical simu-lation；temperature field；residual stress；welding distortionFormation and microstructure of ultrasonic-assisted friction stir lap welding dissimilar Al/Ti alloys MAO Zhendong1， WU Shuanglian1， LIU Xuesong2 (1. CSR Qingdao Sifang Co., Ltd., Qingdao 266111, China；2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China). pp 145-148 Abstract:This work used ultrasonic-assisted friction stir lap welding to join dissimilar Al/Ti alloys. The effect of ultrasonic vibration on joint formation and microstructure was mainly studied. Results show that void appeared inside the joint when the ultrasonic vibration was applied on the Al sheet. Defect-free joint was obtained when the ultrasonic vibration was applied on the Ti sheet. Ultrasonic vibration could enhance the diffusion at the Al/Ti interface, which was beneficial for joint mechanical properties. The thickness of the diffusion layer was rather thin at the rotating speed of 300 r/min. An intermetallic compound with a thickness of 1 µm was obtained at the rotating speed of 500 r/min. The application of ultrasonic could significantly increase the failure load of the joint.Key words: ultrasonic；friction stir lap welding；de-fect；intermetallic compoundsEffects of heat input on microstructure and mechanical properties of copper/steel bimetal by microzone meltingLI Zhen1， QI Yahang1， GAO Peng2， ZHOU Tietao1 (1. College of Materials Science and Engineering, Beihang University, Beijing 100191, China；2. Beijing Aero Engine Control System Co., Ltd. Beijing 102200, China). pp 149-153 Abstract:Copper/steel bimetal materials were obtained with cladding tin bronze on steel substrates by microzone melting. The changing of steels substrate temperature and microzone cooling velocity were simulated by ANSYS. Microstructure and mechanical properties of different region were investigated by optical microscopy(OM), X-ray diffraction(XRD), electron probe microanalysis(EPMA) and micro hardness tester. The results show that as the surfacing process went on, the temperature of the steels substrate increased obviously from 20 °C to 433 °C. The cooling speed decreased from 2 070 K/s to 336 K/s and the hardness of the surfacing layer decreased from 199 HV to 137 HV. The initial peripheral Tin-Bronze coating consisted of αCu, Pb and αFe, which were the product of the Cu-Fe liquid phase separation having a characteristic of metastable liquid phase separation. The grain size of αCu increased from 11.2 μm to 53.4 μm.Key words: tin-bronze；heat input；microzone melt-ing；microstructureA visual model of welding robot based on CNN deep learning LI Hexi1， HAN Xinle1， FANG Zaojun2 (1. Intelligent Manufacturing Department, Wuyi University,2019, Vol. 40, No. 2TRANSACTIONS OF THE CHINA WELDING INSTITUTION VII。
