Electron-Beam Welding Joint Strength of Dissimilar Materials

This paper provides an in-depth discussion of the joint strength of electron beam welding of dissimilar materials.The effect of welding parameters and material properties on the joint strength was analyzed,and an argument for the optimal parameter combination is presented.Electron-beam welding technology offers several advantages,including high energy density and the ability to create fine weld seams.However,it also presents certain challenges,such as the complexity of welding parameters and the potential generation of brittle phases.The analysis conducted in this paper holds significant importance in enhancing the quality and efficiency of dissimilar material welding processes.

Microstructure and mechanical properties of butt joints of QCr0.8/1Cr21Ni5Ti equal-thickness dissimilar materials by electron beam welding

Butt joints of QCr0.8/1Cr21Ni5Ti equal-thickness dissimilar materials were obtained by electron beam welding with fixed accelerating voltage 60 kV and focus current ~1.99 A , changed electron beam current and welding velocity. Microstructure and composition of the EBW joint were investigated by means of optical micrography and EDX analysis, mechanical properties of the joint were also tested. The results show that joint’s macrostructure was divided into three zones: top weld zone near QCr0.8 and bottom weld zone consisting of Cu(ss.Fe) with a certain amount of dispersedly distributed (α+ε) mixed microstructure, middle weld zone consisting of (α+ε) microstructure with a small amount of Cu(ss.Fe) particles. Morphological inhomogeneous macrostructure and uneven chemical compostion of QCr0.8/1Cr21Ni5Ti joint by EBW are the most important factor to result in decreasing joining strength.

Development of processing windows for friction stir spot welding of aluminium Al5052/copper C27200 dissimilar materials

Friction stir spot welding technique was used to join dissimilar combinations of aluminium alloy(Al5052)with copperalloy(C27200)and friction stir spot welding windows such as tool rotational speed–dwell time and tool rotational speed?plungedepth diagrams for effective joining of these materials were developed.Using a central composite design model,empirical relationswere developed to predict the changes in tensile shear failure load values and interface hardness of the joints with three processparameters such as tool rotational speed,plunge depth and dwell time.The adequacy of the developed model was verified usingANOVA analysis at95%confidence level.Response surface methodology was used to optimize the developed model to maximizetensile strength and minimize interface hardness.A high tensile shear failure load value of3850N and low interface hardness valueof HV81was observed for joints made under optimum conditions,and validation experiments confirmed the high predictability ofthe developed model with error less than2%.The operating windows developed shall act as reference maps for future designengineers in choosing appropriate friction stir spot welding process parameter values to obtain good joints.

Review on friction stir welding of dissimilar magnesium and aluminum alloys: Scientometric analysis and strategies for achieving high-quality joints

Magnesium and aluminum alloys continually attract interest as lightweight structural materials for transport applications. However, joining these dissimilar alloys is very challenging. The main obstacle that hinders progress in dissimilar Mg-Al joining is the formation of brittle intermetallic compounds(IMCs). As a solid-state joining technique, FSW is an excellent candidate to attenuate the deleterious IMC effects in dissimilar Al-Mg joining due to the inherent low heat inputs involved in the process. However, the IMCs, namely Al_(3)Mg_(2) and Al_(12)Mg_(17) phases, have also been reported to form during Al-Mg dissimilar FSW;their amount and thickness depend on the heat input involved;thus,the weld parameters used. Since the heat dissipated in the material during the welding process significantly affects the amount of IMCs,the heat input during FSW should be kept as low as possible to control and reduce the amount of IMCs. This review aims to critically discuss and evaluate the studies conducted in the dissimilar Al/Mg FSW through a scientometric analysis and also with a focus on the strategies recently applied to enhance joint quality. The scientometric analysis showed that the main research directions in Mg/Al FSW are the technological weldability of aluminum and magnesium during FSW, structural morphology, and mechanical properties of dissimilar welded joints. Considering the scope of application of the aforementioned joints, the low share of articles dealing with environmental degradation and operational cracking is surprising. This might be attributed to the need for well-developed strategies for obtaining high-quality and sustainable joints for applications. Thus, the second part of this review is conventional, focusing mainly on the new strategies for obtaining high-quality Mg/Al joints. It can be concluded that in addition to the necessity to optimum welding parameters to suppress the excessive heat to limit the amount and thickness of IMC formed and improve the overall joint quality, strategies such as using Zn interlayer, electric current assisted FSW(EAFSW), ultrasonic vibration FSW(UVa FSW), are considered effective in the elimination, reduction, and fragmentation of the brittle IMCs.

Materials flow and phase transformation in friction stir welding of Al 6013/Mg

Material flow and phase transformation were studied at the interface of dissimilar joint between Al 6013 and Mg, produced by stir friction welding （FSW） experiments. Defect-free weld was obtained when aluminum and magnesium were placed in the advancing side and retreating side respectively and the tool was placed 1 mm off the weld centerline into the aluminum side. In order to understand the material flow during FSW, steel shots were implanted as indexes into the welding path. After welding, using X-ray images, secondary positions of the steel shots were evaluated. It was revealed that steel shots implanted in advancing side were penetrated from the advancing side into the retreating side, whereas the shots implanted in the retreating side remained in the retreating side, without penetrating into the advancing side. The welded specimens were also heat treated. The effects of heat treatment on the mechanical properties of the welds and the formation of new intermetallic layers were investigated. Two intermetallic compounds, Al3Mg2 and Al12Mg17, were formed sequentially at Al6013/Mg interface.

Refill friction stir spot welding (RFSSW): a review of processing, similar/dissimilar materials joining, mechanical properties and fracture mechanism

Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.

Microstructure and mechanical properties of dissimilar Al-Cu joints by friction stir welding

Dissimilar friction stir welding between 1060 aluminum alloy and annealed pure copper sheet with a thickness of 3 mm was investigated. Sound weld was obtained at a rotational speed of 1050 r/min and a welding speed of 30 mm/min. Intercalation structure formed at the crown and Cu/weld nugget （WN） area promotes interracial diffusion and metallurgical bonding of aluminum and copper. However, corrosion morphology reveals the weak bonding mechanism of internal interface, which causes the joint failing across the interface with a brittle-ductile mixed fracture mode. The tensile strength of the joint is 148 MPa, which is higher than that of the aluminum matrix. Crystal defects and grain refinement by severely plastic deformation during friction stir welding facilitate short circuit diffusion and thus accelerate the formation of A14Cu9 and A12Cu intermetallic compounds （IMCs）. XRD results show that A14Cu9 is mainly in Cu/WN transition zone. The high dislocation density and formation of dislocation loops are the major reasons of hardness increase in the WN.

Interface microstructure and formation mechanism of ultrasonic spot welding for Al-Ti dissimilar metals

The present study focuses on interface microstructure and joint formation.AA6061 aluminum alloy(Al)and commercial pure titanium(Ti)joints were welded by ultrasonic spot welding(USW).The welding energy was 1100-3200 J.The Al-Ti joint appearance and interface microstructure were observed mainly via optical microscopy and field emission scanning electron microscopy.Results indicated that a good joint can be achieved only with proper welding energy of 2150 J.No significant intermetallic compound(IMC)was found under all conditions.The high energy barriers of Al-Ti and difficulties in diffusion were the main reasons for the absence of IMC according to kinetic analysis.The heat input is crucial for the material plastic flow and bonding area,which plays an important role in the joint formation.

Joining Technology of Dissimilar Materials for Automotive Components(Ⅱ)

Joining techniques of dissimilar materials for lightweight multi-material automotive body structure were discussed. The joining of 1 .4 mm thickness steel and 2 mm thickness of Al were performed by the new method that is hybrid laser welding system. After aluminum and steel were welded by laser hybrid welding process, the micro-structure investment and the micro-hardness test were carried out. Hybrid laser welding promises a bright future in joining technology of dissimilar materials for automotive components.

Joining Performance and Microstructure of the 2024/7075 Aluminium Alloys Welded Joints by Vaporizing Foil Actuator Welding

Vaporizing foil actuator welding(VFAW) was used for joining 2024-T3 and 7075-T6 aluminum alloy sheets, and the resulting joint microstructure was analyzed. 2024/7075 aluminum alloy pairs with suitable processing parameters can be prepared by using VFAW. Dynamic preform addresses the poor formability problem of target material and advantage of VFAW on dissimilar materials in some conditions. But with standoff sheet inserting in the flyer and target, 2024/7075 welded pairs gets the better weld strength, compared with flyer preformed method. The microstructure of the circular weld area of the welded joint showed a wave interface, in which a thin melt layer formed at the center and edge parts. The crystal grains near the bonding interface were remarkably elongated and refined. Therefore, the joining of the 2024/7075 pairs was facilitated through plastic forming and melting.

Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding （FSW） has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy （AA6351 T6-AA5083 Hlll）joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength （UTS） of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology （RSM） and the identified optimum FSW welding parameters were reported.

The Influence of Friction Time on the Joint Interface and Mechanical Properties in Dissimilar Friction Welds

The welding of dissimilar materials is one of the challenging issues in the fabrication industry to obtain required quality welds using fusion welding methods.However,some processes recently improved interface bonding with low joint strength.Unfortunately,the major intermetallic compounds could not alleviate from the joint interface.Alternatively,solid-state welding methods revealed fewer intermetallics at the joint interface for dissimilar material welds.Among them,friction welding was chosen to join incompatible materials with the necessary properties successfully.Friction time is a critical parameter for obtaining strong welds through friction welding,apart from friction pressure,forging pressure,forging time,and rotational speed.Variability of friction time can change the strength of friction by changing mechanical properties such as tensile strength.This change of tensile strength is typically influenced by the intermixing region,dependent on friction time.In this experiment,carbon steel and stainless steel have been friction welded to test the impact of friction time on the joint interface where the substrate’s faying surface meets.This interface consists of the intermixing region of the two materials on which the friction welding is performed.The results showed an interesting variation in tensile strength,with varying friction time.The width of the intermixing zone increased gradually with friction time until and decreased with the further increasing.The strength of the welds obtained was the highest of 730 MPa at a friction time of 4 s and fell as friction time’s increased value after 4 s.

SA508-3/690异种金属焊接接头显微组织及裂纹形成机理

镍基焊材52M因具有优异的抗晶间腐蚀性和耐蚀性,被广泛应用在核电站关键部位的焊接。通过焊条电弧焊用焊材52M焊接低合金钢SA508Gr.3Cl.2和镍基Inconel690合金。结合光学显微镜和扫描电子显微镜分析熔合边界附近的微观组织、成分分布及析出相,探究其对熔敷金属内裂纹形成及硬度变化的影响。结果表明:隔离层熔合边界附近形成Ⅰ型边界、Ⅱ型边界、半岛状组织及岛状组织;S、Nb、Mo元素在局部晶界偏析发生共晶反应引起液化,进而导致在熔敷金属中形成少量结晶裂纹;由于Nb、Mo、Cr等元素的固溶强化作用,熔敷金属的显微硬度略高于两侧母材。

FeCrNiAlCu中间层铝/铜电阻点焊接头的组织性能

采用FeCrNiAlCu高熵合金粉末作为中间层,对2A16铝合金/T2紫铜进行电阻点焊,研究高熵合金粉末对接头显微组织和力学性能的影响。结果表明:高熵合金粉末与液态铝合金存在元素相互扩散现象,并且反应生成富Al的固溶体过渡层。铜侧界面存在两层相结构组织,分别为富Al的固溶体层以及由Al_(2)Cu化合物组成的金属间化合物层(Intermetallic compound,IMC),部分固溶体颗粒与母材形成机械咬合。在焊接电流大小为20~32 kA时,接头的拉伸强度随焊接电流的增加先增加后减小;电流大小为25 kA时,接头的拉伸强度最高,达到1.64 kN,较无中间层的接头提升了30%;接头的断裂发生在铜侧界面处。

外加能场辅助搅拌摩擦焊研究现状

搅拌摩擦焊作为先进固相连接技术,广泛应用于航空航天等领域,轻质高强材料及异种材料连接对常规搅拌摩擦焊的发展提出了新的挑战.近年来,外加能场辅助搅拌摩擦焊技术的兴起有效地解决了异种材料连接中塑化程度不匹配和界面金属间化合物导致接头脆化的问题.同时,这一技术也为解决高熔点材料流变应力大、塑性变形能力差以及焊具磨损严重、焊接效率低等问题提供了新的思路.文中综述了外加能场辅助搅拌摩擦焊的研究现状,包括感应加热、激光加热、电流加热、电弧加热和超声辅助等,从过程产热、材料流动、组织性能调控和耦合作用机制等方面分析了热能和机械能对接头微观组织和性能的影响规律,同时对未来的研究方向进行展望.

铝/铜蓝-红激光复合焊接头组织及性能

为实现动力电池的高效可靠焊接,文中采用蓝-红复合激光进行了1050 Al/T2 Cu搭接焊,分析了激光功率对接头显微组织、相分布、力学性能及导电性能的影响规律.结果表明,铝/铜搭接接头焊缝表面平整,截面呈现T形,PB(蓝光功率)保持300 W,PR(红光功率)在700~1400 W区间内增加,铜侧熔深由60μm增大到1000μm,在PR=800 W时实现良好的冶金结合.焊缝组织由Al固溶体、Al-Cu共晶相和Al_(2)Cu金属间化合物组成,随激光功率增大,焊缝局部出现Al_(4)Cu_(9)相,边缘出现AlCu,Al_(4)Cu_(9)和AlCu_(3)相.在PR=800 W下抗剪强度达到最高108.6 MPa,接触电阻达到最小94μΩ,裂纹由两极交界处Al_(2)Cu区域萌生,沿焊缝边缘由外层Al_(2)Cu区扩展到底部Al固溶体和Al-Cu共晶区交界处,断裂形式为解理断裂.

铝/镁异种材料搅拌摩擦焊工艺参数优化及组织特征分析

利用光学显微镜和电子背散射衍射仪研究1060铝/AZ31B镁异种材料搅拌摩擦焊接头的组织特征,并采用Box-Behnken方法建立响应面模型,对焊接工艺参数偏置量ρ、转速ω、焊速v进行优化。结果表明:热输入过高或过低时,接头焊核区的铝、镁两种材料混合不充分,甚至会产生孔洞;搅拌针偏置量会影响受搅拌的铝和镁材料的体积,当搅拌针偏置时铝和镁材料体积不均匀,也会导致焊核区的铝和镁混合不充分。通过分析响应面模型,结果显示焊速对接头抗拉强度影响最大,优化的工艺参数为ρ=0 mm、ω=1200 r/min、v=150 mm/min,此时接头的抗拉强度较高,其预测值为95.7 MPa。在该焊接工艺参数下,接头焊核区无缺陷且材料混合充分,组织呈现出良好的机械互锁特征,且焊核区因发生动态再结晶,得到均匀细小的组织,接头的实测抗拉强度为96.1 MPa,与响应面模型预测值基本吻合。

铝-钢异种材料回填式搅拌摩擦点焊接头界面连接机制与力学性能研究

以5754铝合金与DC04钢为研究对象,进行了铝板在上的回填式搅拌摩擦点焊试验,研究了搅拌套下扎深度对铝-钢界面微观组织特征与接头力学性能的影响。结果表明,当搅拌套未扎入下层钢板时,冶金结合为铝-钢界面的主要连接机制。当搅拌套扎入下层钢板时,铝-钢界面同时发生机械咬合与冶金结合,其中,机械咬合主要发生在搅拌套作用区。通过工艺优化得出最优工艺参数为:转速2000 r/min、焊速0.5 mm/s,搅拌套下扎深度1.45 mm,此时接头最大拉剪失效载荷达5105 N。

制氢转化炉上尾管加强接头频繁开裂原因分析及对策

某炼化企业制氢转化炉2010年升级改造后,不同炉管的加强接头与上尾管焊口位置先后出现了5次开裂,造成制氢装置非计划停工。通过对运行环境、高温氢腐蚀、热膨胀应力、结构应力、异种钢焊接、弹簧支吊架等多方面开展深入分析,发现泄漏的原因主要是加强接头与上尾管连接焊缝局部高应力区发生了应力松弛开裂,同时,工艺参数控制不严格加遽了开裂速度。2021年通过实施炉管材质升级、稳定工艺运行环境、严控施工质量等措施,没有再出现过开裂的情况,彻底消除了炉管运行过程中的安全隐患,保障了设备的本质安全和装置的长周期运行。

基于不同焊材的超高强钢与BS700高强钢焊接接头裂纹的试验研究

采用熔化极活性气体保护焊对抗拉强度大于1600 MPa的超高强钢与抗拉强度大于760 MPa的BS700高强钢进行焊接时,组合接头焊缝易出现焊接裂纹,为解决该问题,使用直径1.0 mm的ER70-G焊材或ER307Mo焊材,在打底焊接电流160~180 A、电压21~24 V,盖面焊接电流190~210 A、电压23~26 V条件下开展了焊接对比试验。工艺性和焊接性试验结果表明,使用ER307Mo焊材焊接的试样弯曲性能明显优于使用ER70-G焊材焊接的试样;使用ER70-G焊材焊接的试样焊缝存在未贯穿的微裂纹,焊缝断面裂纹率达到35.29%;使用ER307Mo焊材焊接的试样焊缝断面未发现裂纹。ER307Mo焊材更适合超高强钢与BS700高强钢的焊接。试验解决了超高强钢与BS700高强钢组合接头的开裂问题,为抗拉强度相差较大的异种高强钢的焊接提供了解决方案。