基于激光——MIG复合热源的5A02铝合金/镀锌钢熔——钎焊

基于激光--MIG复合热源焊接技术实现了5A02铝合金/镀锌钢异种金属板材的优质、高效熔-钎焊接,并对焊缝的成形、接头性能及微观结构作了分析.分析结果表明,该焊接技术可以实现5A02铝合金/镀锌钢的高速熔-钎焊接,最高焊接速度可达5 m/min,焊接接头中镀锌钢母材未发生熔化,铝焊缝与镀锌钢母材为钎焊连接;焊接接头的抗拉强度可达153.1 Mpa,约为5A02铝合金母材抗拉强度的75.7%,接近于该铝合金熔化焊接头的强度;拉伸试验中试样断裂在焊缝铝合金母材热影响区,接头的断裂主要是塑性断裂,但有脆性断裂的痕迹.对接头的组织和结构进行分析表明:焊缝钎接界面处生成了一薄层Al-Fe金属间化合物,化合物层的平均厚度约为1.51μm,生成的金属间化合物主要为Fe3Al、FeAl2、Fe2A15、FeAl3,并且在这些化合物的周围会产生Si元素的富集.     

厚板5083铝合金搅拌摩擦焊接头沿厚度方向组织与力学性能

目前,国内外对100 mm以上厚度的铝合金搅拌摩擦焊研究较少。针对110 mm厚5083铝合金(o态)板材进行搅拌摩擦焊双面对接试验。焊后试样进行焊缝表面渗透检测、接头力学性能检测,对焊缝横截面、拉伸试样断口进行光学显微镜金相组织观测、扫面电镜观测。结果表明,试验所得焊接接头质量良好,焊缝表面无渗漏,焊缝内部没有孔洞、隧道等缺陷;试样抗拉伸强度平均值达到母材的98%以上,屈服强度平均值达到母材90%以上,伸长率平均值分别达到母材的75.5%和82.4%,抗拉伸强度沿厚度方向呈现先降低后升高的“V”型趋势;焊缝横截面微观组织无缺陷,晶粒分布均匀并有Mg元素富集相析出;接头断裂机制为混合断裂,从焊缝表面至底部,断裂机制由韧性断裂向脆性断裂趋势发展。试验将110 mm厚铝合金搅拌摩擦焊接头沿厚度方向进行性能分析与研究。     

5056铝合金/镀锌钢预置涂粉激光熔钎焊组织及性能研究

针对铝/钢焊接的技术难点,采用预置金属粉末的方法,对5056铝合金与ST04Z镀锌钢板进行CO2激光搭接熔钎焊,分析熔钎焊接头成形、接头连接界面的显微组织及其力学性能。结果表明,选择合适的焊接参数,涂粉后能够实现铝合金与镀锌钢的优质连接;熔钎焊接头没有明显的针状Al-Fe金属间化合物向熔化区析出,且过渡层最大厚度小于10μm,在熔化区边缘和熔化区与铝合金结合处熔钎焊根部出现两个富Zn区,Si、Zn、Mn、Mg等元素与Fe和Al或直接形成化合物,或形成固溶物,抑制了Al与Fe直接接触形成脆硬的金属间化合物;接头拉伸试样断裂形式有母材热影响区断裂和焊缝处断裂两种,焊缝处断裂面在铝熔化区一侧,接头平均机械抗力达190 N/mm,约为母材的85.2%。采用此方法可减小铝/钢熔钎接界面过渡层厚度,获得力学性能良好的熔钎焊接头。     

铝合金与高强钢激光-电弧焊铆复合连接机制研究

为实现6061铝合金和Q460高强钢的优质连接,采用激光诱导电弧复合热源对已通过阶梯型铆钉实现预连接的6061铝合金板和Q460高强钢板进行搭接焊试验。分析焊铆复合连接方法下接头的力学性能,断裂模式以及横截面的宏观和微观形貌。结果表明,在铆钉和复合热源的共同作用下,焊铆复合连接接头由3个承载区域组成,分别为钢板和铆钉形成的对接接头,钢板,铆钉以及铝合金板形成的铝-钢连接区以及铆钉侧壁和铝合金板侧壁形成的铝-钢界面。铝-钢连接区的金属间化合物以富Fe的Fe Al相和Fe3Al相为主。在最佳工艺参数下,焊铆复合连接接头的拉剪载荷达到6.2 k N。拉伸断口呈现出纽扣式断裂、母材基体断裂以及拉拔式断裂3种断裂模式,后两种断裂具有更高的韧性和塑性。阶梯型铆钉和激光-电弧复合热源的协同作用可以实现铝合金和高强钢的优质连接。     

6061铝合金激光填丝焊接接头的组织与力学性能

通过显微硬度计、拉伸试验机、扫描电镜和X射线衍射仪等研究了激光填丝焊接6mm厚6061铝合金接头的显微组织和力学性能。结果表明:焊缝中心区域的显微组织为等轴晶,由α-Al固溶体组成,无β(Mg_2Si)强化相析出,近熔合区的焊缝组织为柱状晶;焊接接头焊缝的硬度最低,约为73HV,母材的硬度最高,约为110HV,随着距焊缝中心距离的增大,热影响区的硬度先呈波浪式增大,在距焊缝中心2.2~3.8 mm处有所下降,此外为热影响区软化区,在距焊缝中心3.8~4.4mm处又快速增大;焊接接头的抗拉强度为234 MPa,约为母材的71%,高于熔化极惰性气体保护焊接接头的;焊接接头均在焊缝处断裂,接头与母材均为韧性断裂。     

铝/镀锌钢薄板异种金属CMT熔钎焊接头组织与力学性能

采用冷金属过渡方法对铝合金和镀锌钢板进行了熔钎焊连接,使用扫描电镜、能谱分析和拉伸试验分析了接头的截面形貌、组织特征、焊接缺陷及力学性能。试验结果表明,铝合金和镀锌钢能得到成形美观、性能良好的搭接接头。对焊缝金属的组织特征分析表明,焊接接头由熔化区、中心界面区、过渡界面区和富锌区组成,在焊缝金属和镀锌板的界面区形成厚度为3～4μm的金属间化合物层(主要成分为Fe3Al、FeAl2、Fe2Al5和FeAl3),富锌区由富铝的固溶体和残留的锌组成。在进行拉伸试验时,断裂发生在热影响区,接头强度为204MPa。     

薄板铝合金空间曲线焊缝CMT焊接试验研究

针对薄板铝合金三维曲线焊缝较大的残余应力和焊接变形,进行了冷金属过渡(CMT)无垫板自动焊试验研究,分析了电流、焊接速度、弧长修正、保护气流量对焊接过程的影响,进行了接头拉伸性能试验及焊缝微观组织研究,并焊接了变形小的产品。结果表明,利用合理的焊接参数,可实现厚度1.5 mm的5A06铝合金的无垫板CMT焊接,焊缝成形稳定均匀,焊接接头抗拉强度值达到347 MPa,接头断裂位置在热影响区。无垫板CMT焊接技术可用于薄板铝合金空间曲线焊缝的焊接。     

基于原位拉伸的CrMoV钢焊接接头局部力学性能研究

采用微拉伸试验研究了CrMoV钢焊接接头焊缝金属的局部力学性能,并对焊缝金属进行了微观组织观察和显微硬度测试。结果表明,焊缝金属呈现不均匀的微观组织分布;焊缝金属环向试样的拉伸强度要大于径向和轴向试样的拉伸强度,而焊缝中心所取试样的拉伸强度要小于焊道上所取试样的拉伸强度。结合金相分析得到,焊接接头焊缝金属最薄弱的部位在焊缝中心等轴晶区。     

铝合金型材的静轴肩倾斜搅拌摩擦焊接头性能

采用静止轴肩搅拌摩擦焊装置对6005A铝合金型材进行焊接,并对焊后接头进行拉伸与弯曲的检测,观测了焊缝与拉伸断口横截面组织,结果表明：静轴肩焊缝表面平整无弧纹;倾斜焊接可避免焊缝表面沟槽;焊接速率1 m/min、转速2100 r/min时,接头的抗拉强度达到母材的73%,屈服强度达到母材的55%;转速1700 r/min、1800 r/min时,试样背弯出现裂纹,随着转速的升高,裂纹消失。焊缝横截面出现S曲线,试样断裂机制为韧性断裂。随着转速提高,组织的细化程度与分布均匀程度升高。     

钢铝异种金属的低能量焊接法

传统电弧焊法焊接钢铝异种金属时,会在过渡区生成Fe-Al金属间化合物层,其硬度高、韧性低,降低了接头性能。基于机械作用的低能量电弧焊接方法,在短路期间采用机械作用促使熔滴过渡,热输入量低,可有效抑制金属间化合物的晶体长大,该种工艺可以采用常规4047焊丝实现铝和镀锌板的焊接。对焊缝金属的金相分析表明,钢一侧为钎焊,铝一侧为熔焊。通过金相及扫描电镜观察发现,在焊缝金属和镀锌板的界面区形成的金属间化合物层,主要成分为Fe2Al5和FeAl3,金属间化合物层的厚度减小到3～4 μm。在界面区主要含有3种元素,分别为Fe、Al和Si,没有Zn元素。拉伸试验表明,焊缝接头在铝合金热影响区断裂,且强度值高于铝合金母材强度的70%,接头强度基本满足使用要求。     

搅拌摩擦焊缝类型对接头拉伸性能及断裂特征的影响

采用三种不同针长的搅拌头对6082-T6铝合金板材进行焊接,获取三种类型的焊缝,即未透对接焊缝、已透对接焊缝和对-搭组合焊缝,通过对焊缝金相观察、拉伸测试和断口分析,得到焊缝类型对接头拉伸性能及断裂特征的影响规律。不同类型焊缝的表面成形区别不大,但内部成形各有特点。未透对接焊缝根部界面处形成未焊合缺陷;已透对接焊缝中无缺陷;对-搭组合焊缝后退侧和前进侧形成“钩状”缺陷。拉伸测试表明,未透对接接头拉伸性能最低,裂纹在未焊合处产生并沿焊核区扩展,接头下部呈现剪切断裂特征,接头上部呈现准解理和剪切混合断裂特征;已透对接接头拉伸性能最高,断裂位置位于前进侧热机影响区,断口呈现出典型的剪切断裂特征;对-搭组合接头拉伸性能居中,裂纹在前进侧“钩状”缺陷处产生并沿焊核区扩展,断口形貌与未透对接接头相似。     

Fundamental study on electron beam weld sections and strengths using AA6061-T6 aluminum alloy plate

This study was carried out to establish an electron beam welding process for a nuclear fuel plate assembly fabrication. A preliminary investigation for plate fuel fabrication was conducted with a consideration of weld performance using AA6061-T6 aluminum alloy made by the electron beam welding process. The optimum welding parameters for the fuel plate assembly were obtained in terms of the accelerating voltage, beam current and welding time. The soundness of the weld region between the side plate and the end fitting for the fuel plate assembly was proven by the intact of the weld metal on the fractured surfaces. The integrity of the welds by the electron beam welding process was also confirmed by the results of the tensile test, an examination of the cross sections and the fracture surfaces of the welded specimens.     

Influences of rotation speed on microstructures and mechanical properties of 6061-T6 aluminum alloy joints fabricated by self-reacting friction stir welding tool

A 6061-T6 aluminum alloy was self-reacting friction stir welded by using the specially designed tool with unequal shoulder diameters at a constant welding speed of 150 mm/min to investigate the effect of rotation speed on microstructure and mechanical properties of the joints. Excessive flash on the bottom surface of the joint and groove defects on both surfaces of the joint were formed when the lower shoulder diameter was much smaller. The suitable shoulder sizes were determined as 16 and 18 mm in lower shoulder diameter and upper shoulder diameter, respectively. The grain size and the dislocation density in the weld nugget zone (WNZ) increased with increasing rotation speed. The tensile strength of joints first increased with increasing rotating speed and then decreased remarkably as a result of the formation of void defect. The joints welded at lower rotation speeds were fractured in the thermal mechanically affected zone (TMAZ). However, the fracture locations of the defect-free joints were changed to the heat affected zone (HAZ) at higher rotation speeds.     

Weld temperature effects during friction stir welding of dissimilar aluminum alloys 6061-t6 and 7075-t6

The objective of this work is to establish nominal friction stir [butt] welding process parameters for joining 4.76-mm-thick aluminum alloys 6061-T6 and 7075-T6 and to improve the joint quality via programmed tool offsets. In addition, dynamic tool–workpiece interface temperatures are measured during welding and used to explain the effects of alloy placement and weld tool offset from the joint. Weld tool offsets into the retreating side AA7075 increase the measured tensile strength of the dissimilar joint. The increased joint strength is facilitated by lower average weld temperatures with increasing amount of AA7075 stirred into the nugget.     

6061-T6铝合金MIG焊接头微区拉伸性能表征及接头拉伸性能的有限元仿真

建立了6061-T6铝合金MIG焊接接头微区拉伸性能测试的高精度等效试验方法;采用有限元模拟了焊接过程的温度变化情况,建立了温度与接头各微区拉伸性能的关系;获得了可表征接头各微区材料性能的参数,验证了将接头等效为不同热状态材料所建立的精细模型对接头性能预测的可靠性.结果表明:微区温度场、焊缝熔池形貌和拉伸性能的仿真模拟...     

焊接顺序对6061-T6铝合金矩形焊缝焊接残余应力及变形量的影响

以热弹塑性有限元法为基础,结合热-力耦合的算法建立有限元模型,采用Abaqus软件对薄壁6061-T6铝合金矩形型材进行焊接模拟;模拟了不同焊接顺序对铝合金型材残余应力及焊接变形量的影响,得到了最优的焊接顺序。结果表明:在矩形焊接时焊缝所在平面上产生的最大残余应力为拉应力;选择对称焊接工艺可以有效降低铝合金型材焊接后的残余应力,增强焊件的焊后稳定性;从较长的焊接路径开始焊接,能够减小焊接变形量。     

电极形状对铝-钢点焊接头组织及力学性能的影响*

研究6061-T6铝合金-SUS301L不锈钢异种金属电阻点焊接头的微观组织特点及电极形状的影响规律。结果表明,铝-钢点焊接头具有熔-钎焊特征,铝合金熔核由α-Al胞状晶、胞状树枝晶和树枝晶组成,铝/钢界面层具有双层结构,靠近铝熔核侧主要为细针状Fe₄Al₁₃,靠近不锈钢侧主要为Fe₂Al₅金属间化合物,接头主要为界面断裂模式,铝/钢界面是点焊接头最薄弱的区域。电极形状对铝合金-不锈钢点焊接头具有明显的影响。获得的优化电极形状为：不锈钢侧为圆形平面电极,电极端面直径为10 mm;铝合金侧为球面电极,球面半径为35 mm。在优化电极条件下,铝合金-不锈钢点焊接头的熔核直径、拉剪力及压痕率分别为7.5 mm、4.7 kN和13.5%。与采用F型电极相比,其熔核直径和拉剪力分别提高53.1%和56.7%,压痕率降低47.3%。因此,采用优化电极更有利于改善铝合金-不锈钢电阻点焊接头的力学性能及表面质量。     

Effect of welding processes on tensile properties of AA6061 aluminium alloy joints

The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.     

2A14厚板铝合金SSFSW角焊缝接头组织及性能

采用自主研制搅拌针长度为8.5mm的静止轴肩搅拌工具和2A14-T4厚板铝合金进行150°角焊缝接头静止轴肩搅拌摩擦焊工艺试验,探讨焊接工艺参数对接头组织和力学性能的影响规律。结果表明:在500~700r/min主轴转速与40~100mm/min焊接速度范围内均可获得表面光滑无内部缺陷的角焊缝接头,其外观尺寸可精确控制基本无残余焊接角变形。焊缝区主要由焊核(Stir zone,SZ)组成,SZ形状类似搅拌针圆锥台状或椭圆状、其宽度沿厚度方向分布比较均匀;热力影响区(Thermal mechanical affected zone,TMAZ)及热影响区(Heat affected zone,HAZ)宽度明显较小。焊缝区硬度分布具有明显不均匀特征,最薄弱区位于TMAZ与HAZ的交界处。主轴转速变化对焊缝区平均硬度影响较小,但随着焊接速度增加其平均硬度明显增大。角焊缝前进侧等效拉伸强度大于后退侧,等效拉伸强度随转速增加而减小,焊速的增大而增大。在500r/min-100mm/min焊接工艺下所得到的接头等效拉伸强度最高,可达到母材的79.24%。在拉-剪复合承载模式下,角焊缝拉伸试样宏观塑性变形很小呈现脆性断裂特征。     

Thermo-mechanical finite element model of friction stir welding of dissimilar alloys

A thermo-mechanical finite element model is developed based on Coupled Eulerian Lagrangian method to simulate the friction stir welding of dissimilar Al6061-T6 and Al5083-O aluminum alloys using different tool pin profiles. The model is validated using published measured temperatures and weld microstructure. The finite element results show that maximum temperatures at the weld joint were below the materials’ melting point. Placing the harder alloy (Al6061-T6) at advancing side led to a decrease in maximum process temperature and strain rate, but increased tool reaction loads. Featured tool pin produced better material mixing resulting in enhanced joint quality with reduced volumetric defects.