2195铝锂合金超声振动辅助搅拌摩擦焊接工艺研究

采用新型超声振动辅助搅拌摩擦焊接设备实现了4 mm厚的2195铝锂合金轧制板的焊接,比较和分析了施加超声对焊缝宏观金相组织、显微硬度与接头拉伸性能的影响,研究了工艺参数对铝锂合金超声振动辅助搅拌摩擦焊缝成形及接头力学性能的影响规律.结果表明:在相同工艺参数条件下,施加超声振动能量能够改善2195铝锂合金搅拌摩擦焊接成形性,促使焊核区塑性材料流动增强,同时减少甚至消除常规搅拌摩擦焊接头内部的孔洞缺陷;在焊缝的上部及中部,由于超声的作用,焊核区的显微硬度得以提高,而焊缝底部变化不大;接头的断口均呈现出韧性断裂模式,施加超声振动能量后的接头的伸长率得以提高,其断口韧窝更加细小均匀;在所研究的工艺参数范围内,接头的最高抗拉强度为282.8 MPa,最大伸长率为11.5％.在转速为600 r/min,焊接速率为225 mm/min条件下,施加超声使接头抗拉强度提高了17.5 MPa,伸长率提高了3.7％.     

铝 / 钢异种金属搅拌摩擦焊及其研究进展

铝/钢异种金属连接结构在国防领域和国民生产、生活中更加广泛应用的前提,是获得良好的接头综合性能,但铝/钢焊接时易出现裂纹、金属间化合物等,严重影响了焊接接头质量。摩擦焊作为一种低温高效的固相连接方法,在新材料连接、高性能装备制造等领域受到了高度重视。其中,搅拌摩擦焊由于其可焊接头形式丰富而被重点关注。从搅拌摩擦焊的接头形式、工艺参数、力学性能及界面组织4个方面,分别介绍了铝/钢搅拌摩擦焊的研究进展,为其深入研究提供依据。     

铝/钢异种材料搅拌摩擦焊研究进展

由于铝、钢的物理化学性质存在巨大差异,铝/钢的连接是焊接领域的难点问题。搅拌摩擦焊是低热输入的固态连接方法,能够有效控制铝/钢金属间化合物的生长,且搅拌针强烈的搅拌作用可增加铝/钢异种材料机械咬合程度,得到高质量的铝/钢焊接接头,铝/钢搅拌摩擦焊已经成为了焊接领域的热点问题。文中综述了铝/钢搅拌摩擦焊国内外研究现状,涉及到接头形式、焊缝成形、焊接工艺和力学性能,着重介绍了铝/钢搅拌摩擦焊接头的连接机制,并围绕铝/钢搅拌摩擦焊存在的两大问题,对铝/钢搅拌摩擦焊新技术进行总结,并进一步提出了铝/钢搅拌摩擦焊的基础研究方向。     

铝 / 镁异种金属搅拌摩擦焊研究现状及发展趋势

为进一步优化焊接工艺,提高铝/镁异种金属搅拌摩擦焊接头的性能,促进铝/镁异种金属结构在航空航天、轨道交通、汽车工业等领域的广泛应用,综述了近5年来国内外铝/镁异种金属搅拌摩擦焊接的最新研究成果,对焊接工艺参数、接头的力学性能、微观组织以及异种金属搅拌摩擦焊的新工艺进行了总结和分析。国内外大量研究结果表明,通过选择合适的工艺参数、改变搅拌针的偏移,可以获得抗拉强度较高、焊缝成形良好的铝/镁异种金属搅拌摩擦焊接头,焊缝中存在的金属间化合物是导致焊接接头性能不能满足工程应用的主要因素,但目前对于搅拌摩擦焊接过程中金属间化合物的产生、分布规律缺乏深入研究。     

超声振动强化搅拌摩擦焊技术的研究进展

针对笔者团队前期发明的超声振动强化搅拌摩擦焊(Ultrasonic Vibration enhanced FSW,UVeFSW)新工艺,从设备研发(超声振动装置的设计、超声振动参数的表征)、工艺试验(焊缝成形、微观组织、显微硬度、拉伸性能、疲劳性能)与机理探索(焊接载荷、焊接热循环、材料流动和组织演变)3方面,综述了UVeFSW新工艺的研究进展。结果表明,通过直接向搅拌头前方的待焊接工件上施加超声振动能场,改善焊缝成形,减少或消除焊接缺陷,拓宽焊接工艺参数窗口以及提高接头性能。     

铝/钢搅拌摩擦辅助铆接接头界面特性研究

目的探究搅拌摩擦辅助铆接铝/钢接头界面的结合特征,解决传统铆接力学性能较低的问题。方法采用搅拌摩擦焊技术实现了对3mm厚不锈钢板和4mm厚的铝合金板的搭接点焊,采用OM及SEM对铝/钢接头界面结合情况进行分析,并利用EDS对界面处元素分布进行分析。结果搅拌头转速1180 r/min、焊接时间120 s、下压量0.2 mm时,铝/钢接头界面结合较好,平均拉剪力达到6519 N,且在铝/钢界面处产生FeAl金属间化合物。受摩擦热作用的影响,位于下板的铝母材晶粒发生长大变粗,铝铆钉与铝板结合紧密,铝铆钉与铝板的结合情况受搅拌头压力的影响更为显著。结论搅拌摩擦辅助铆接铝/钢异种合金,实现了铆钉与铝板和钢板的有效冶金结合,在铝钢结合界面处存在原子的互扩散现象,且有相应的金属间化合物生成。     

超声对铝/镁异质合金搅拌摩擦焊接成形的影响

开展了厚度为4 mm的6061铝合金/AZ31B镁合金板的搅拌摩擦对接工艺实验,对比分析了常规搅拌摩擦焊(FSW)和超声振动强化搅拌摩擦焊(UVeFSW)的焊缝横截面与水平截面的材料流动情况、界面金属间化合物厚度、机械锁合程度以及接头拉伸性能等,探究了超声振动的作用机理。结果表明：超声振动能够促进接头不同部位的材料流动和热量传输,从而减小甚至消除焊接缺陷;施加超声振动后,铝/镁界面处的金属间化合物均有所减薄,同时界面机械锁合程度也均有所增强,因此UVeFSW接头的抗拉强度相比于同一工艺参数时FSW接头有所提高,施加超声振动后接头的最高抗拉强度达到了174.20 MPa。     

超声对铝/镁异质合金搅拌摩擦焊接成形的影响

开展了厚度为4 mm的6061铝合金/AZ31B镁合金板的搅拌摩擦对接工艺实验,对比分析了常规搅拌摩擦焊(FSW)和超声振动强化搅拌摩擦焊(UVeFSW)的焊缝横截面与水平截面的材料流动情况、界面金属间化合物厚度、机械锁合程度以及接头拉伸性能等,探究了超声振动的作用机理。结果表明：超声振动能够促进接头不同部位的材料流动和热量传输,从而减小甚至消除焊接缺陷;施加超声振动后,铝/镁界面处的金属间化合物均有所减薄,同时界面机械锁合程度也均有所增强,因此UVeFSW接头的抗拉强度相比于同一工艺参数时FSW接头有所提高,施加超声振动后接头的最高抗拉强度达到了174.20 MPa。     

旋转速度与焊接速度对铝铜异种材料搅拌摩擦焊接头成形的影响

目的为了获得较好的铝铜异种材料搅拌摩擦焊焊缝,研究旋转速度与焊接速度对焊缝成形的影响规律。方法采用对接的方式对4mm厚的纯铝和紫铜进行搅拌摩擦焊,对比了不同旋转速度和焊接速度对铝铜异种金属焊缝表面的影响,并对焊缝内部成形变化进行了分析。结果旋转速度和焊接速度对焊缝的成形影响较大,当旋转速度为1200 r/min,焊接速度为10 mm/min时,焊缝表面成形美观,焊缝表面相对较为光滑,焊缝内部存在相互交叠的片层结构和漩涡状结构,焊缝内部未见明显缺陷;与旋转速度1200 r/min,焊接速度10mm/min相比,在焊接旋转速度减小或者焊接速度变大时,由于焊接热输入减小,造成焊缝表面出现沟槽、孔洞等焊接缺陷,同时搅拌针的旋转搅拌作用影响焊缝成形和焊缝内部缺陷的产生。结论选择合适的旋转速度和焊接速度能够获得宏观成形较好和内部缺陷较少的焊缝。     

铝/镀锌钢搅拌摩擦铆焊接头组织与力学性能

为实现铝钢之间的优质连接,采用搅拌摩擦铆焊新方法对6061铝合金和DP600镀锌钢进行搭接点焊,利用扫描电子显微镜、能谱仪及拉伸试验对接头的微观组织及力学性能进行了研究.结果表明:接头成形平整美观,中心没有匙孔;接头包含铆接区和扩散区,其中在铆接区铝合金以铝柱的形式嵌入到钢板的圆孔中,形成了一个"铝铆钉",底部有富铝的α固溶体偏聚,圆孔四周形成扩散区,铝和钢形成了冶金结合,依靠金属间化合物Fe Al3连接在一起;接头有3种断裂形式,在最佳工艺参数下接头的抗剪力达到8.2 k N;铝柱上断口的微观形貌是被拉长的韧窝,扩散区的断口由灰色基体和白色颗粒组成.     

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.     

Fatigue behavior of dissimilar friction stir welds between cast and wrought aluminum alloys

Cast aluminum alloy, AC4CH-T6, and wrought aluminum alloy, A6061-T6, were joined by means of friction stir welding (FSW) technique. The effect of microstructure and post heat treatment on fatigue behavior of the dissimilar joints was investigated. Near the weld centre, Vickers hardness was lower than in the parent metals and the hardness minima were observed along the trace route of FSW tool’s shoulder edge. Tensile fracture took place on A6061 side where the hardness was minimal, resulting in the lower static strength of the dissimilar joints than AC4CH or A6061. Fatigue fracture occurred on AC4CH side due to casting defects and the fatigue strength of the dissimilar joints was similar to that of AC4CH, but lower than that of A6061. Friction stir process (FSP) and post heat treatment successfully improved the fatigue strength of the dissimilar joints up to that of the parent metal, A6061. __________ Translated from Problemy Prochnosti, No. 1, pp. 150–154, January–February, 2008.     

铝合金搅拌摩擦焊超声检测研究进展EI北大核心CSCD

铝合金搅拌摩擦焊(friction stir welding, FSW)焊接参数选择不当将会产生隧道孔、未焊透(lack of penetration, LOP)和吻接等取向复杂、细微紧贴的缺陷。首先,本文简述了FSW焊缝与典型缺陷特征,总结了超声检测时面临纵向分辨力低、缺陷表征不完整、材料与缺陷声阻抗接近和灵敏度不足等难点。随后,从常规超声、超声衍射时差法(time-of-flight diffraction, TOFD)、相控阵超声检测技术和其他超声检测技术等方面综述了现有的铝合金FSW超声检测研究工作。最后,结合超声信号处理方法和机器学习方法对研究前景进行展望:可以通过分析和提取信号特征,进一步提升超声检测分辨力和信噪比,并实现取向复杂缺陷和细微紧贴缺陷的精准辨识与定量。     

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.     

热电耦合对铝/钢连续驱动摩擦焊接头组织的影响机理

采用连续驱动摩擦焊技术焊接纯铝1060/Q235低碳钢异质接头,开展两个周期(30天/60天)热电耦合实验(静载392 N+高温300 ℃+直流60 A),研究热电耦合对铝/钢异质接头焊缝微观组织、力学性能及界面生长的影响。结果表明：原始态接头界面径向金属间化合物(IMCs)层厚度不均匀,中心区域无明显IMCs生成。热电耦合30天后界面中心生成宽度为0.3~0.5 μm且以颗粒状由钢侧向铝侧弥散分布的IMCs层,整体拉伸断裂在铝母材的热力影响区。热电耦合60天后IMCs层与钢侧之间出现腐蚀沟槽,IMCs破碎,钢侧无裂纹产生,铝侧形成大量由IMCs层向铝母材内部扩展的裂纹和孔洞,焊缝及裂纹尖端处成分偏析,整体拉伸断裂在焊缝处。界面腐蚀和失效速率与界面IMCs层的厚度成正比,即v_center＜v_1/2R＜v_2/3R。由于原始态接头界面组织不均匀以及热电耦合实验过程中界面不同位置组织生长速率的差异,使得热电耦合后接头界面2/3R位置出现不同断裂形貌的分界线,2/3R内侧以准解理断裂方式为主,2/3R外侧为韧窝断裂和准解理断裂的综合结果。     

Refill friction stir spot welding of 5083-O aluminum alloy

In this work,refill friction stir spot welding(RFSSW) was used to weld 2 mm-thick 5083-O alloy.The Box–Behnken experimental design was used to investigate the effect of welding parameters on the joint lap shear property.Results showed that a surface indentation of 0.3 mm effectively eliminated the welding defects.Microhardness of the stir zone(SZ) was higher than that of the base material(BM) and the hardness decreased with increasing the heat input during welding.The optimum failure load of 7.72 k N was obtained when using rotating speed of 2300 rpm,plunge depth of 2.4 mm and refilling time of 3.5 s.Three fracture modes were obtained during the lap shear test and all were affected by the hook defect.     

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.     

基于热力耦合模型铝合金搅拌摩擦焊接顺序优化仿真分析

基于所建立的搅拌摩擦焊接过程热输入模型和热力耦合有限元分析模型,对带圆孔铝合金板的搅拌摩擦焊接顺序进行了有限元研究,并得到了焊接过程中不同焊接方案下的温度、瞬态应力变化曲线以及焊后残余变形。通过综合比较可以看出,从两边向中间焊的方案2优于从中间向两边焊的方案1和从左向右的顺序焊接的方案3。此外,有限元模型求解结果和实验测量数据具有相当好的吻合。     

Application of the hybrid process ultrasound enhanced friction stir welding on dissimilar aluminum/dual‐phase steel and aluminum/magnesium joints

Friction stir welding as a solid‐state joining method with its comparatively low process temperatures is suitable for joining dissimilar materials like aluminum/magnesium or aluminum/steel. Such hybrid joints are of great interest regarding lightweight efforts in different industrial fields like the transportation area. The present work investigates the influence of additionally transmitted power ultrasound during the friction stir welding on the joint properties of EN AC‐48000/AZ91 and EN AW‐6061/DP600. Therefore, conventional friction stir welding was continuously compared to ultrasound enhanced friction stir welding. Light microscopic analysis and nondestructive testing of the joints using x‐ray and high frequency ultrasound show different morphologies of the nugget for the aluminum/magnesium joints as well as differences in the amount and size of steel particles in the nugget of aluminum/steel joints. Scanning electron microcopy proves differences in the thickness of continuous intermetallic layers for the aluminum/steel joints realized with and without power ultrasound. Regarding the tensile strength of the joints the power ultrasound leads to increased joint strengths for EN AC‐48000/AZ91 joints compared to a decrease for EN AW‐6061/DP600 joints. Corrosion investigations show an influence of the ultrasound power on the corrosion properties of EN AC‐48000/AZ91 joints which is attributed to a changed aluminum content in the nugget region. Because of the great potential difference between the magnesium and the nugget phase the transitional area exhibits strong galvanic corrosion. For EN AW‐6061/DP600 joints an increased corrosion caused by galvanic effects is not expected as the potentials of the EN AW‐6061 aluminum alloy and DP600 steel are very similar.