焊接参数对铁素体不锈钢搅拌摩擦焊接头组织及性能的影响

对4mm厚T4003铁素体不锈钢进行搅拌摩擦焊接工艺实验,研究焊接参数对接头组织特征、硬度分布及常温和低温冲击韧性的影响。结果表明:接头搅拌区和热力影响区由铁素体和马氏体双相组织构成;接头搅拌区组织沿试样厚度方向存在非均质性,且随转速的降低及焊接速率的增加越发显著;转速从150r/min增加至250r/min,前进侧热力影响区组织呈现小梯度过渡趋势,无明显变形拉长特征。焊缝硬度分布相对均匀,其最高硬度为290HV,约为母材的1.87倍。焊接参数和温度对接头的冲击吸收功有较大影响:常温(20℃)下,热影响区为母材的90%～92%,搅拌区为母材的85%～103%;低温(-20℃)下,热影响区为母材的87%～97%,搅拌区为母材的82%～95%,表明焊缝区仍具有较好强韧匹配。     

镁合金搅拌摩擦焊接工艺参数优化

为了优化镁合金搅拌摩擦焊接工艺参数,对5 mm厚镁合金AZ31B板材的搅拌摩擦焊接技术进行了试验研究,利用SN比实验设计,对镁合金AZ31B搅拌摩擦焊接工艺参数进行了方差分析,优化了搅拌头的材料、结构,最终确定搅拌头的材料为W6Mo5Cr4V2,结构为凹面圆台形.轴肩尺寸为12 mm.探针的根部直径为5.5 mm,端部直径为2.5 mm,长度为4.7 mm.获得镁合金AZ31B搅拌摩擦焊的工艺参数显著性顺序为旋转速度、横向速度和压力;确定了镁合金AZ31B搅拌摩擦焊的最优工艺参数为1500 r/min、47.5 mm/min、3kN.     

Modeling of friction stir welding process for tools design

A three-dimensional friction stir welding (FSW) process model has been developed based on fluid mechanics. The material transport in the welding process has been regarded as a laminar, viscous, and non-Newtonian liquid that flows past a rotating pin. A criterion to divide the weld zone has been given on the basis of cooperation of velocity field and viscosity field. That is, the η₀-easy-flow zone that existed near the tool pin corresponded to the weld nugget zone; the area between the η₀-easy-flow zone and η₁-viscosity band is corresponded to the thermal-mechanical affected zone (TMAZ). The model gives some useful information to improve the understanding of material flow in FSW through the simulation result of velocity distribution. In order to appraise the friction stir pin design, three kinds of pin geometry, one is column pin, the second is taper pin, and the last one is screw threaded taper pin, were used in the model. The pin geometry seriously affected the simulation result of velocity distribution in the η₀-easy-flow zone. The velocity distribution in the η₀-easy-flow zone can be considered as the criterion of optimizing friction stir tool design. This study will benefit to direct the friction stir tool design.     

焊接参数对搅拌摩擦焊接质量的影响

采用基于固体力学的有限元方法建立了搅拌摩擦焊接过程的三维数值模型,研究了在焊接参数不同的情况下搅拌摩擦焊接过程中力学特征的变化．数值模拟结果和试验结果都表明,等效塑性应变能近似地反映焊接构件焊缝区域材料显微结构的演化,较高的搅拌头转速和较低的焊速有利于提高焊缝的质量．焊接构件特定的等效塑性应变等值线可以较好的对应不同焊接区域的边界．随着搅拌头转速的提高,等效塑性应变随之增大,但搅拌探针与焊接构件交界面上的接触压力随之减小．等效塑性应变随着搅拌头平移速度的增大而减小．     

Microstructure and enhanced atomic diffusion of friction stir welding aluminium/steel joints

Lap joints of friction stir welding between aluminium and stainless steel sheets were conducted using a welding tool with a cutting pin. The atomic diffusion of Fe–Al system during the severe plastic deformation was investigated. The interfacial microstructure and metallurgical reaction was analysed. The metallurgical reaction layers were identified as a compounds containing a phase of Al₃Fe, partial solid solution of Fe and Al, and amorphous with a thickness of 0.9–3.3?μm which depending on the process parameters. The interdiffusion coefficient between Al and Fe atoms is about 4 orders of magnitude compared with that under thermal equilibrium state. The nanocrystalline and partial amorphous were formed near the interface which may caused by the enhanced atomic diffusion.     

2195铝锂合金搅拌摩擦焊接头盐雾腐蚀行为研究

本文研究了厚度为8 mm的2195铝锂合金母材及搅拌摩擦焊接头在3.5wt.％NaCl介质中的盐雾腐蚀行为,计算了不同腐蚀周期下的腐蚀速率,并通过OM、SEM、TEM观察分析母材与焊核区的腐蚀微观形貌.结果 表明:2195铝锂合金母材及搅拌摩擦焊接头在3.5％ NaCl腐蚀介质中的主要腐蚀形式为点蚀,随时间的延长发展为...     

Effect of welding parameters on microstructure and mechanical properties of AA7075‐T6 friction stir welded joints

The effects of advancing speed and rotational speed on the microstructure and the mechanical properties of friction stir welded 7075‐T6 aluminium alloy sheets were studied. The fatigue strength of sound joints was measured and compared to tensile testing results. Macrographs and microhardness maps were carried out to reveal the microstructure transformations. Fractographic observations were made to identify the failure mechanisms. The effects of welding parameters on the fatigue strength are discussed in terms of welding pitch k (mm/rev) and heat input (J/mm). At a high welding pitch, crack initiation at the root of the circular grooves left by the tool on the weld surface is the most detrimental failure mechanism. As the size and the depth of the grooves are related to the welding pitch, the fatigue strength increases when the welding pitch is reduced. However, when the heat input is excessive, the failure is caused by sub‐surface defects produced after abnormal stirring and/or by softening of the heat‐affected zone. Lateral lips on the weld surface edges also have an effect on the fatigue strength for intermediate welding pitch values.     

Spot friction stir welding of low carbon steel plates preheated by high frequency induction

In this study, high frequency induction heating assisted spot friction stir welding was applied to 1.6 mm thick S12C low carbon steel plates. With the same welding parameter including an applied load of 2500 kg, rotation speed of 800 rpm and dwell time of 2 s, the average grain size in the stir zone slightly increased from 12.9 μm for the welds without preheating to 14.8 μm when 10 s preheating was used. However, larger joint interface was formed within the stir zone of the welds with preheating and therefore the bonding strength can be significantly increased. As a result, the shear tensile load of the joint increased from 8 kN to12.4 kN with preheating and the joint fractured through the plug failure mode rather than interfacial failure mode. It was revealed that the frictional heat generated between the rotating tool and the work-piece can be reduced to obtain sound welds by means of high frequency induction preheating.     

Effect of processing parameters on static strength of dissimilar friction stir spot welds between different aluminium alloys

The effect of processing parameters on static strength and fracture mechanisms of dissimilar friction stir spot welds between different aluminium alloys was studied. Tensile shear strength increased with decreasing tool rotational speed and increasing tool holding time, while cross tension strength decreased with increasing both parameters. Two fracture modes were observed: nugget shear fracture and mixed mode fracture under tensile shear loading, and debonding and pull‐out of the nugget under cross tension loading. Based on experimental observation, the dependence of static strength on processing parameters and the occurrence of different fracture modes were discussed.     

The effect of weld parameters on friction stir welding of brass plates

More successful results have been obtained in butt‐ and overlap‐joining of Al‐alloy plates by a recently developed solid state joining technique, namely friction stir welding (FSW), than in more conventional fusion welding processes. In this joining technique, no fusion takes place in the joint area of the plates welded. This novel joining method also offers the potential to weld some other materials rather than Al‐alloys, such as Mg‐alloys, brasses and low strength steels. In this study, the applicability of friction stir welding to brasses, namely 90 %Cu‐10 %Zn and 70 %Cu‐30 %Zn alloys, has been investigated. The joint performance was determined by conducting optical microscopy, microhardness mesurements and mechanical testing (e.g. tensile and bend tests). The effect of welding speed on the joint quality at a given rotational speed of the stirring pin (i.e. 1600 rpm) was also determined for both alloys. The highest joint performances were obtained at a welding speed of 210 mm/min for both alloys.     

率相关材料在搅拌摩擦焊接过程中的行为分析

为研究金属粘性效应时的搅拌摩擦焊接材料流动行为,采用率相关本构描述搅拌摩擦焊接过程中的材料行为,并与非率相关材料模型的计算结果进行了对比.结果显示,由于考虑了金属的粘性效应.用率相关材料模型模拟搅拌摩擦焊接过程能更好地反映材料流动行为的本质.在搅拌摩擦焊接中,材料沿搅拌头切向方向的运动构成了搅拌摩擦焊接构件材料流动的主要形式.焊接构件-搅拌头接触面上的接触压力在搅拌头前方较大,在搅拌头后方较小,这一规律在率相关模型中更为明显.搅拌头前方材料在搅拌头的挤压之下向远离搅拌头的方向运动,而搅拌头后方的材料要填充由于搅拌头的移动而留下的空间,这一过程是保证搅拌摩擦焊接顺利完成的一个主要因素.因此,用率相关模型模拟搅拌摩擦焊接过程中的材料力学行为更为接近真实情况.     

Production of tailor-welded blanks by vertical compensation friction stir welding technique

An attempt was made for the first time to fabricate tailor-welded blanks (TWBs) through the feasibility of selective alloying in the solid state of vertical compensation friction stir welding (VCFSW) technique. The results revealed that the production of TWBs by VCFSW technique had higher homogeneity without any defects when compared to the production of TWBs by conventional FSW process at constant tool rotational speed 2000?rpm, traverse speed 20?mm?min^?1 and an inclination angle 2.5°. The maximum mechanical properties of the fabricated TWBs were obtained when the width of compensation strip 1.5?mm was used. The fracture surface of TWB at the width of compensation strip 1.5?mm showed ductile fracture mode.     

铝/钢异种金属的超声振动强化搅拌摩擦焊接工艺

采用新型超声振动强化搅拌摩擦焊接工艺实现了6061-T6铝合金以及QP980高强钢的搭接焊,对比分析了有无超声作用下,接头的宏观形貌、微观组织和拉伸剪切性能,同时研究了超声振动对焊接载荷的影响。结果表明:焊接前对母材施加超声振动,可以起到软化母材的作用,促进了材料的塑性流动,扩大了铝/钢界面区和焊核区,使更多的钢颗粒随搅拌针旋转进入铝合金侧,在界面区边缘形成钩状结构,进而提高了接头的失效载荷;超声改变了FSW接头断裂位置和断口形貌,提高了接头力学性能,在本实验工艺参数范围内,接头最大的平均失效载荷为4.99 kN;当焊接速度为90 mm/min,下压量为0.1 mm时,施加超声振动使接头的平均失效载荷提高了0.98 kN,拉剪性能提升28.24%;施加超声振动后轴向力F_z、搅拌头扭矩M_t和主轴输出功率分别下降2.46%,6.44%和4.59%。     

Relationship between base metal properties and friction stir welding process parameters

Friction stir welding (FSW) is a solid state welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds.     

Analysis of process parameters effects on friction stir welding of dissimilar aluminum alloy to advanced high strength steel

Thin sheets of aluminum alloy 6061-T6 and one type of Advanced high strength steel, transformation induced plasticity (TRIP) steel have been successfully butt joined using friction stir welding (FSW) technique. The maximum ultimate tensile strength can reach 85% of the base aluminum alloy. Intermetallic compound (IMC) layer of FeAl or Fe₃Al with thickness of less than 1 μm was formed at the Al–Fe interface in the advancing side, which can actually contribute to the joint strength. Tensile tests and scanning electron microscopy (SEM) results indicate that the weld nugget can be considered as aluminum matrix composite, which is enhanced by dispersed sheared-off steel fragments encompassed by a thin intermetallic layer or simply intermetallic particles. Effects of process parameters on the joint microstructure evolution were analyzed based on mechanical welding force and temperature that have been measured during the welding process.     

刚柔协作3CD/2RPU-SPR搅拌摩擦焊机器人研究

为满足搅拌摩擦焊技术的要求,解决搅拌摩擦焊机器人在顶锻力承受以及焊接灵活性方面存在的不足,在三自由度2RPU-SPR搅拌摩擦焊机器人基础上增加了3根绳索,设计了一种刚柔协作3CD/2RPU-SPR搅拌摩擦焊机器人。基于运动学建模,运用封闭矢量法分别计算了3CD/2RPU-SPR搅拌摩擦焊机器人刚性部分与绳索部分的位置逆解;运用求导法求得了机器人刚性部分与绳索部分的速度雅克比矩阵,并运用特征长度法将雅克比矩阵无量纲化,基于求得的速度无量纲雅克比矩阵,利用MATLAB软件分别对添加绳索前后的搅拌摩擦焊机器人的各项运动学性能指标进行编程求解;应用遗传算法对3CD/2RPU-SPR搅拌摩擦焊机器人的性能指标进行优化,通过设定最优个体系数、种群数目、遗传进化次数,对满足3CD/2RPU-SPR搅拌摩擦焊接机器人全域刚度以及全域灵巧性的结构参数进行寻优求解。结果表明:3CD/2RPU-SPR搅拌摩擦焊机器人的承载力、灵巧性、全域灵巧性、刚度、全域刚度等性能指标均有所提高,且在综合考虑灵巧性以及刚度的优质工作空间内运动连续,说明3CD/2RPU-SPR搅拌摩擦焊机器人相较于2RPU-SPR搅拌摩擦焊机器人能够承受更大的顶锻力,且运动灵活性有所提高。通过遗传算法优化后找到符合3CD/2RPU-SPR搅拌摩擦焊机器人全域灵巧性以及全域刚度的10组结构参数,在综合考虑搅拌摩擦焊接工况下,从10组结构参数中选取最优的一组作为搅拌摩擦焊机器人的结构参数,在该结构参数下,机器人性能指标有所提高,更适合完成搅拌摩擦焊接工作。研究为提高机器人搅拌摩擦焊接质量提供了理论依据。     

Fatigue performance of hybrid overlap friction stir welding and adhesive bonding of an Al‐Mg‐Cu alloy

The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid‐state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024‐T3 Al‐Mg‐Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints.     

Effect of friction stir welding process parameters on the tensile strength of dissimilar aluminum alloy AA2024-T3 and AA7075-T6 joints

This work investigates the influence of friction stir welding parameters on the mechanical properties of the dissimilar joint between AA2024-T3 and AA7075-T6. Experiments are conducted consistent with the three-level face-centered composite design. Response surface methodology is used to develop the regression model for predicting the tensile strength of the joints. The analysis of variance technique is used to access the adequacy of the developed model. The model is used to study the effect of key operating process parameters namely, tool rotation speed, welding speed and shoulder diameter on the tensile strength of the joints. The results indicate that friction stir welding of aluminum alloys at a tool rotation speed of 1050 min⁻¹, welding speed of 40 mm/min and a shoulder diameter of 17.5 mm would produce defect less joint with high tensile strength.     

轴肩结构对搅拌摩擦焊过程中材料流动的影响

考虑材料参数随温度的变化关系以及搅拌头的实际结构形式,利用ANSYS FLUENT软件对搅拌摩擦焊过程中材料的流动行为进行了数值分析,研究了轴肩结构分别为平面、内凹与同心圆时的材料流动规律.研究表明,当轴肩结构发生变化时,焊件表面及内部的材料流动趋势基本相同;靠近焊件表面的材料流动速度在轴肩结构为同心圆时最大,在轴肩结构为平面时最小.从避免搅拌摩擦焊根部缺陷的角度看,同心圆轴肩的搅拌头优于内凹轴肩,这一规律得到了试验证实.