Microstructural Evolution and Mechanical Behavior of Friction-Stir-Welded DP1180 Advanced Ultrahigh Strength Steel

Friction stir lap welding of a DP1180 advanced ultrahigh strength steel was successfully carried out by using three welding tools with different pin lengths. The effects of the welding heat input and material flow on the microstructure evolution of the joints were analyzed in detail. The relationship between pin length and mechanical properties of lap joints was studied. The results showed that the peak temperatures of all joints exceeded A c3, and martensite phases with similar morphologies were formed in the stir zones. These martensite retained good toughness due to the self-tempering effect. The formation of ferrite and tempered martensite was the main reason for the hardness reduction in heat-affected zone. The mechanical properties of the lap joints were determined by loading mode, features of lap interface and the joint defects. When the stir pin was inserted into the lower sheet with a depth of 0.4 mm, the lap joint exhibited the maximum tensile strength of 12.4 kN.     

半螺纹搅拌针对2024铝合金搅拌摩擦搭接焊力学性能影响

作为影响搅拌摩擦焊（FSW）过程中塑性材料上下流动的重要因素,搅拌针螺纹形貌同样对搅拌摩擦搭接焊（FSLW）的材料流动和力学性能有着重要影响.为研究半螺纹搅拌针对FSLW接头显微组织和力学性能的影响,文中将全螺纹搅拌针和半螺纹搅拌针用于包铝2024铝合金FSLW试验,并对不同搅拌针作用下的FSLW接头的横截面形貌、剪切拉伸载荷、断裂位置等方面进行分析对比.结果表明,半螺纹搅拌针会使钩状缺陷向下弯曲,从而使FSLW接头具有较大的有效板材厚度以及搭接宽度.断裂模式同为剪切断裂,但半螺纹搅拌针作用下的FSLW接头拥有更大的拉断载荷.     

铜/钢异种金属搅拌摩擦焊搭接工艺

采用SKD61模具钢搅拌头对2 mm厚铜/钢异种金属进行搅拌摩擦焊搭接,分析了搭接接头微观组织和力学性能. 结果表明,当搅拌针与钢母材直接接触时,随焊接过程的进行搅拌针不断磨损甚至发生断裂. 焊核区前进侧出现流线区域,在搭接界面结合处形成机械冶金结合. 显微硬度测试显示,铜侧焊核区硬度最高,在搭接界面处硬度分布呈中间高两边低的趋势,接头厚度方向搭接界面处硬度最高. 形成良好结合的搭接接头在拉剪试验中断裂于铜侧热影响区,拉伸断口存在大量韧窝,呈典型韧性断裂模式.     

辅助电流对Cu/Al大功率超声波焊接的影响

为获得更高质量的Cu/Al异质金属接头，开展了Cu/Al电流辅助大功率超声波焊接工艺试验，研究了辅助电流对Cu/Al超声波焊接的界面温度、材料塑性流动、界面中间相分布及接头力学性能的影响。结果表明，复合焊件成型良好，其接头抗拉剪力为3030 N，接头的断裂模式为韧性-脆性复合断裂。在同样的焊接时间0.2 s内，随着电流的增大，Cu/Al界面温度增加，金属塑性流动以及界面扩散也随之增强，这说明辅助电流能明显促进界面冶金；相比长时间0.4 s的超声波焊接，辅助电流能在保证界面温度、材料塑性变形的前提下，能明显减薄了界面IMC层的厚度，这是电流增强Cu/Al接头的主要物理机制。研究结果为优化Cu/Al复合焊接头强度提供了参考。     

Cu/Ti异种金属搅拌摩擦焊搭接接头组织与性能

文中采用搅拌摩擦焊法搭接T2工业紫铜和TA2纯钛,研究了搭接接头的宏观形貌和微观组织结构,并测试了接头力学性能.结果表明,当选用搅拌头旋转频率为800 r/min,焊接速度为40 mm/min的工艺参数配比时,可以获得焊缝表面成形良好,连接界面无缺陷的搭接接头.在焊核区,钛和铜以相间的条带结构形式相互混合、紧密连接在一起,形成了涡流状的钛铜双相金属混合区域,而且某些区域呈现出"机械互锁"的组织形貌.钛铜搭接接头抗剪切力可达到铜母材失效载荷的95%,断裂位置位于搭接接头铜板前进侧,为典型的韧性断裂.     

Ti/Al异种合金搅拌摩擦焊搭接接头的界面特性(英文)

采用搅拌摩擦焊实现TC1钛合金和LF6铝合金异种材料的搭接连接,并对界面特性进行研究。采用所选取的工艺参数均能获得良好的表面成形,但每一种工艺参数下的界面形貌不同。随着焊接速度的增加或搅拌头转速的降低,被搅拌针搅入焊核区的钛合金粒子的数量减少,而且搭接接头的抗拉载荷也随着焊接速度的提高而降低。当焊接速度为60mm/min、搅拌头旋转速度为1500r/min时,接头的抗拉载荷达到最大值,此时的界面区可以分成三层。搭接接头的显微硬度分布不均匀,焊核中心区的显微硬度值最大,高达HV502。     

DP600/AZ31无匙孔搅拌摩擦点焊塑性金属流动特性及断裂行为研究

在最优焊接参数下,对1 mm DP600镀锌钢板和3 mm AZ31镁板进行无匙孔搅拌摩擦点焊试验,焊后对接头分别进行横切、纵切及层切,采用扫描电镜（SEM）分析焊接接头显微组织和断口形貌.结果表明,镁钢间的混合主要发生在搅拌针作用区域,形成“机械互锁”的组织形貌,有利于增加两种材料的有效接触,形成复相强化;轴肩作用区镁钢间搅拌不明显,界面较平滑,镁钢界面形成了金属化合物以及氧化镁,降低了接头的塑性和韧性.对DP600/AZ31无匙孔搅拌摩擦点焊焊接接头进行拉伸试验,发现焊接接头从搭接界面上断裂,断口呈“脉状花样”,为延性断裂.     

2024-T4超薄铝合金机器人搅拌摩擦焊接头组织及力学性能

机器人作为搅拌摩擦焊系统的载体时,由于其关节采用串联模式进行连接,在焊接过程中关节易发生变形,而变形的释放会导致焊漏等缺陷,制约了机器人搅拌摩擦焊系统在超薄板焊接过程中的应用. 针对上述问题,文中对0.5 mm厚超薄2024-T4铝合金板进行了机器人搅拌摩擦焊工艺研究. 结果表明,增加下压量或提高主轴转速成功实现薄板铝合金焊接,在主轴转速为2 500 r/min,焊接速度为600 ~ 1 000 mm/min工艺参数内,接头强度呈现升高趋势,最高可达408 MPa,达到母材90%. 接头硬度呈双“W”形分布,其断裂形式为韧性断裂.     

Microstructure,static and fatigue properties of refill friction stir spot welded 7075-T6 aluminium alloy using a modified tool

ABSTRACT

Defect-free joints were produced in 2.0?mm thick 7075-T6 Al alloy by refill friction stir spot welding using a modified tool. Weld performance was evaluated in terms of microstructure, interfacial bonding, hardness, static and fatigue strength based on the experimental observations. The results indicated that grain size, interfacial bonding quality and lap shear strength significantly depend on sleeve penetration depth (SPD), with sufficient interfacial bonding and stable lap shear strength achieved when SPD?≥?1.8?mm. The SPD and applied load played a dominant role in determining the static lap shear and fatigue failure mechanisms, respectively. More precisely, the lap shear failure mode was an interfacial failure when SPD?≤?1.8?mm, and nugget pullout when SPD?≥?2.0?mm. The fatigue fracture mode involved nugget pullout under high applied load, while fracture through the parent sheet occurs under medium and lower applied loads.     

A Novel Friction Stir Spot Riveting of Al/Cu Dissimilar Materials

In order to eliminate the disadvantages of the keyhole in conventional friction stir spot welding joint and attain the high-strength lap joint of Al/Cu dissimilar metals,a novel welding technique,named as friction stir spot riveting(FSSR),was proposed.A pinless tool and an extra filling stud were employed.The Al/Cu spot joints without keyhole defect were achieved by the FSSR.A Cu anchor-like structure was formed,which greatly increased the mechanical interlocking between the upper Al sheet and lower Cu sheet.The thin intermetallic compounds containing CuAl2 and CuAl at the Al/Cu interface strength-ened the joining interface between the Al sheet and the Cu stud.Increasing rotating velocity increased frictional heat and plastic deformation and then eliminated the interfacial joining defects.The FSSR joint with the maximum tensile shear load of 3.50 kN was achieved at a rotating velocity of 1800 rpm and a dwell time of 20 s,whose fracture path passed through the softened region of upper Al sheet.In summary,the novel FSSR technique has the advantages of strong mechanical interlock-ing and metallurgical bonding between dissimilar materials,thereby attaining the high-strength spot joint.     

焊接能量对Mg/Ti超声波焊接接头微观组织与力学性能的影响

采用超声波焊接技术对Mg/Ti异种金属进行了焊接,研究了不同焊接能量对接头界面峰值温度、界面形貌、界面原子扩散程度以及力学性能的影响规律。研究发现:Mg/Ti超声波焊接接头整体界面较平直,局部界面有较小起伏,未发现裂纹、未熔合等缺陷,也未看到明显的反应层;随着焊接能量的增大,界面峰值温度升高,原子扩散层厚度增大,连接区面积逐渐增大,接头力学性能得到提高,而能量达到2000J时镁侧母材出现裂纹;接头断裂模式分为界面断裂和纽扣断裂,界面断裂时断裂发生在镁侧扩散层区域和镁侧非扩散层区域。扫描电子显微镜和X射线衍射仪分析表明,Mg/Ti连接界面区域无明显的金属间化合物生成。     

基于涡状搅拌针的2024-T4铝合金搅拌摩擦扩散焊接头成形与断裂载荷

以2024-T4铝合金为对象进行了搅拌摩擦扩散焊试验,首次提出并使用涡状搅拌针,且对比分析了涡状搅拌针数量对横截面形貌、材料流动行为与力学性能的影响. 结果表明,涡状搅拌针作用下的搭接界面未出现明显的弯曲现象,增加涡状针的数量有利于增加焊核区底部的宽度. 当采用4个涡状结构的搅拌针时,发生拉伸断裂模式的搭接接头有效连接宽度与断裂载荷均大于具有6个涡状结构的搅拌针,其值分别为11.74 mm及17 531.83 N.     

Si,Mg对铝/钢熔钎焊焊接接头力学性能的影响

采用脉冲旁路耦合电弧MIG熔钎焊方法,分别采用4043,5356铝合金焊丝对5052铝合金/镀锌钢异种金属进行了搭接焊.通过扫描电镜（SEM）,能谱仪（EDS）,X射线衍射仪（XRD）对铝/钢连接界面、接头断裂行为及断口形貌进行了分析,发现5356铝合金焊丝焊接接头的润湿角要大于4043铝合金焊丝焊接接头的润湿角,合金元素Si既可改变界面反应层金属间化合物的形态同时还可显著减少Fe₂Al₅层的厚度.拉伸试验发现5356铝合金焊丝焊接所得接头主要断裂于界面反应层,属于脆性断裂;4043铝合金焊丝焊接所得接头主要断裂于熔合区,是以韧性断裂为主的混合断裂.通过对4043铝合金焊丝焊接所得接头进行显微硬度测试,发现热影响区组织的显微硬度明显低于其它区域的显微硬度,这导致4043铝合金焊丝焊接接头主要断裂于熔合区.     

Effect of pin rotating speed on lap shear strength of stationary shoulder friction stir lap welded 6005A-T6 aluminum alloy

Stationary shoulder friction stir lap welding (SSFSLW) was successfully used to weld 6005A-T6 aluminum alloy in this paper.Effect of pin rotating speed on cross section morphologies and lap shear strength of the SSFSLW joints were mainly discussed.Results show that joints without flash and shoulder marks can be obtained by the stationary shoulder.Cross section of the SSFSLW joint presents a basin-like morphology and little material loss.By increasing the rotating speed from 1 000 rpm to 1 600 rpm,both effective sheet thickness and lap width increase,while lap shear failure load firstly decreases and then increases.The maximum failure load of 14.05 kN is attained when 1 000 rpm is used.All SSFSLW joints present shear fracture mode.     

铝合金薄板搅拌摩擦焊搭接界面缺陷与接头性能

针对2A12–T4铝合金薄板进行了搅拌摩擦焊搭接试验,研究了焊接参数对缺陷形态与接头性能的影响规律. 结果表明,勾状缺陷具有更大的高度和弯曲角度,最大缺陷高度为上板厚度的12.7%. 随焊接速度增大,缺陷高度减小.随转速提高,勾状缺陷高度先增加后减小,冷搭接缺陷高度呈“V”形变化. 在950 r/min,200 mm/min下接头强度最高,接头系数可达84%. 维氏显微硬度分布呈“W”形,上板出现接头软化,焊核区下部硬度高于上部硬度. 冷搭接缺陷是影响接头性能的主要因素,由于有效搭接宽度较小,接头断裂方式为沿搭接面的剪切断裂.     

Q235钢搅拌摩擦焊接头微观组织与力学性能分析

在焊接速度为100 mm/min和搅拌头转速为450 r/min的工艺参数下,采用钨铼合金搅拌头对3 mm厚Q235钢进行了搅拌摩擦焊试验,并对接头的微观组织及力学性能进行了研究. 结果表明,在该工艺参数下可以获得表面无缺陷、成形良好的焊缝. 焊后搅拌头表现出一定程度的磨损及氧化. 接头截面各区域承受不同的热力联合作用,经历了不同的组织转变过程,但均保持铁素体和珠光体组织. 接头显微硬度最大值位于焊核区. 接头拉伸断裂位置处于热影响区,拉伸断口呈韧性断裂特征.     

Macrostructures and mechanical properties of ultrasonic-assisted friction stir welding joint of 2024-T3 aluminium alloy

In friction stir welding of aluminum alloys, tunnel defect may occur due to insufficient plastic material flow caused by lower heat input in the weld region. The inadequacy in heat input is due to improper selection of friction stir welding tool and process parameters. Ultimately, such defects degrade the properties of weld and may pose serious concerns towards the integrity and safety of the weld component. In order to improve the properties of weld joints, an ultrasonic-assisted friction stir welding device has been configured where ultrasonic energy is transferred from an ultrasonic unit directly into one of the workpieces near the tool. Using this configuration, ultrasonic-assisted friction stir welding was conducted on 6 mm thick 2024-T3 aluminum alloy sheets. The macrostructure and mechanical properties of these welds were compared with the welds of this alloy prepared by conventional friction stir welding using identical process parameters. The results show that the welding speed can be increased while satisfactory weld quality is still ensured. The ultrasonic energy transferred in this configuration could enlarge the volume of weld nugget zone. Also, the influence of ultrasonic energy on the suppression or elimination of the tunnel defect is quite apparent. However, any beneficial effects of ultrasonic vibration on the tensile strength and the elongation of the joint were less obvious in this configuration.     

镁铝异种金属搅拌摩擦焊搭接接头组织与性能分析

采用搅拌摩擦焊技术对异种金属铝合金5083和镁合金AZ31进行了搭接焊试验.对接头的力学性能、组织形貌及断口形貌进行了观察和分析.结果表明,在铝板置于上层、搅拌针长度小于铝板板厚的情况下,使用合适的工艺参数,这两种轻合金可以获得抗剪性能良好、界面结合紧密、无缺陷的搭接接头,从而使镁板和铝板通过由一定金属间化合物组成的界面区过渡层形成了良好的连接;接头都断裂于界面结合处,铝侧是由塑性撕裂导致的"小坑"组成,而镁侧主要为河流状花样;在界面中心区出现了明显的硬度升高现象.     

Study of joining mechanism of ABS polymer and steel/aluminum by resistance spot welding

The joining of metal and polymer is an increasingly important method to get lightweight components in the development of manufacturing industry nowadays. In this article,metal and polymer lap joint was achieved by means of resistance spot welding( RSW)and ultrasonic assistance welding( UAW). The joining mechanism of lap joint was analyzed by OM,TEM on microstructure at the interface of lap joints and XPS and IR spectra was discussed based on the following different ones: mechanical-interlocking,diffusion bond and coordination bond. The results showed that it was the combined action that played an important role in the effective joining work. Besides,ultrasonic assistance was used in the study to aid welding process based on its high-frequency ultrasonic vibration,which made joints shaping better and improved tensile strength visibly contrast to joints with the same lower heat input parameters.     

轴肩下压量对搅拌摩擦焊搭接接头力学性能的影响

采用表面为右螺纹圆柱型搅拌针的搅拌头对3mm厚LY12铝合金进行了搅拌摩擦焊搭接试验,研究了轴肩下压量对接头界面迁移和搭接接头力学性能的影响.结果表明,随轴肩下压量增大,焊缝两侧的搭接界面均向下迁移,其迁移量随下压量的增加而增加,焊缝返回侧的界面迁移量大于前进侧.控制轴肩下压量,当轴肩下压量合适时,焊缝两侧的界面仅发生较小的迁移.当焊缝两侧的界面仅发生较小的迁移量时,搭接接头有较高的抗剪强度,且断裂都发生在上板,呈正断.焊缝两侧的搭接界面向下迁移时,断裂都发生在下板,接头抗剪强度随界面迁移高度的增加而减小,且受拉侧在下板前进侧时,接头的抗剪强度较受拉侧在下板返回侧时的高.