6082铝合金摩擦塞补焊接头微观组织与性能

在不同的焊接转速下,对5 mm厚的6082铝合金进行顶锻式摩擦塞补焊实验研究,分析了塞补焊接头的金属流动性、微观组织、第二相分布、温度场、力学性能、显微硬度以及断口形貌特征。结果表明:塞补焊接头截面上层金属流动性明显优于下层;焊缝根部受摩擦热最低且金属流动性差,使其成为整个塞补焊接头的薄弱区;在摩擦界面区,塞棒大量细密的等轴晶穿插进母材板条状的晶粒中,实现了塞补焊接头的紧密连接;焊接接头不同区域β(Mg_2Si)相的大小、数量及方向均有不同程度的变化;在焊接转速2 200 r/min下,焊接接头力学性能最好,接头抗拉强度达到母材的75%以上,断后伸长率达到了母材的64%以上;焊接接头断裂在塞孔与塞棒之间的摩擦界面区,裂纹从焊缝根部弱连接区域起裂并向焊缝表面扩展,断裂方式为韧性断裂;整个塞补焊接头母材侧热机影响区和热影响区结合处软化最为严重,硬度值在(60±5) HV之间。     

汽车轮辋用钢搅拌摩擦焊接头组织及力学性能

目的 为搅拌摩擦焊在轮辋钢的应用提供理论数据。方法 选用厚度为4.5 mm的江铃汽车V362轮辋钢板B380CL,采用不同的焊接参数,获得搅拌摩擦焊接头,对焊缝宏观成形及微观组织进行分析,研究焊接参数对组织的影响;通过进行拉伸试验和硬度测试,分析焊接参数对焊接接头性能的影响;对接头焊缝进行X-Ray无损探伤。结果 当搅拌头旋转速度为950 r/min,焊接速度分别为37.5, 47.5, 60 mm/min时,均能形成焊接接头。焊接速度为47.5 mm/min时,焊缝宏观成形较好,微观组织无缺陷,微观组织为铁素体和珠光体,抗拉强度最高,超过母材;焊接接头各区域微观组织硬度较母材高,伸长率较焊接速度为37.5 mm/min时的接头高。结论 搅拌摩擦焊实现轮辋钢的对接,该研究中旋转速度950 r/min,焊接速度47.5 mm/min为最佳工艺参数,接头抗拉强度超过母材。     

铝合金搅拌摩擦焊接头微观组织和力学性能分析

目的 研究7020铝合金搅拌摩擦焊(FSW)的结构和机械性能。方法 采用搅拌摩擦焊对铝板进行对接焊试验,具体形式为单面焊双面成型。采用拉伸机和显微维氏硬度仪对试样进行力学性能测试;利用蔡司金相、光谱仪、扫描电子显微镜、X射线衍射仪研究母材和焊接接头的微观组织。结果 在硬度上,母材>热影响区>焊核区,热影响区平均硬度约为94HV,母材平均硬度为99HV,焊核区平均硬度最低为78HV,焊核区出现“S”缺陷,在一定程度上弱化了焊核区性能;7020铝合金搅拌摩擦焊接头的抗拉强度为235 MPa,屈服强度为158 MPa,屈强比为0.67,伸长率为7%,焊接系数可以达到73.8%;母材的抗拉强度为325 MPa,屈服强度为278 MPa,屈强比为0.86,伸长率为25%;焊接接头中心显微组织主要由胞状树枝晶体组成,显微结晶依次呈现为平面晶、胞状晶、树枝状晶、等轴晶;铝合金母材和焊接接头的金属相组成均为α?Al+Mg2Si;焊接接头断口呈现比较明显的韧性断裂特征。结论 铝合金搅拌摩擦焊可以获得性能比较优良的焊接接头,为其他铝合金材料的FSW焊接提供技术参考。     

Ag对热电耦合作用下铝/钢摩擦焊接头界面组织演变的影响

目的 解决铝/钢摩擦焊接头在热电耦合后失效的问题,探究过渡元素对热电耦合后接头力学性能与界面组织的影响机理。方法 采用刷镀法在Q235钢棒端面添加过渡元素Ag并与1060纯铝棒进行连续驱动摩擦焊接,与未添加Ag的接头一起开展为期56 d、静载40 kg、高温300 ℃、直流60 A的热电耦合实验,对比分析热电耦合影响下未添加Ag与添加Ag两种接头力学性能与界面微观组织的变化。结果 经过热电耦合处理后的接头界面发生脆断,其抗拉强度为原始接头的96.2%,伸长量为原始接头的28.9％,界面金属间化合物出现裂纹、孔洞等缺陷。添加过渡元素Ag后,接头抗拉强度为原始接头的98.2%,断裂部位为铝母材并出现颈缩,界面金属间化合物层未出现裂纹、孔洞等缺陷。结论 在为期56 d、静载40 kg、高温300 ℃、直流60 A的热电耦合作用下,添加过渡元素Ag的铝/钢接头可以维持原始接头的力学性能和界面组织。     

6005A-T6铝合金搅拌摩擦焊接头组织与力学性能特征

采用光学显微镜、扫描电子显微镜、透射电子显微镜、拉伸实验机和显微硬度计对6005A铝合金搅拌摩擦焊接头的微观组织及力学性能进行了研究。结果表明:焊核区为细小的等轴晶,几乎所有粒子溶于基体;热机械影响区呈现为被拉长的畸变晶粒,且存在大量的位错;热影响区的组织明显粗化,处于过时效状态。与母材相比,搅拌摩擦焊接头的强度及伸长率均有下降趋势,且接头出现软化,最小硬度值出现在前进侧的热影响区内。搅拌头旋转速率为1200r/min、焊接速率为200mm/min时可获得优质接头,抗拉强度达到母材强度的72%,伸长率达到母材的69%。     

旋转速度对高强度钢Q&P980搅拌摩擦焊接头组织与性能的影响

为了促进高强度钢在汽车领域的应用,解决高强度钢在采用常规熔化焊进行焊接时出现的问题,利用搅拌摩擦焊接技术对1. 2 mm厚的高强度钢QP980进行焊接试验,并利用激光共聚焦显微镜、扫描电子显微镜、万能试验机和显微硬度计等手段研究旋转速度对高强度钢QP980搅拌摩擦焊接头的微观组织和力学性能的影响。研究发现,在不同旋转速度下均获得了没有缺陷的焊缝,接头组织呈典型的"碗状"组织形貌。旋转速度为200 r/min时,接头搅拌区组织仍为马氏体与铁素体组织,但晶粒尺寸相比母材明显细化且马氏体含量相比母材增多。随着旋转速度的提高,马氏体含量会继续增多,旋转速度为400 r/min时搅拌区组织基本全部为马氏体组织,旋转速度为600 r/min时搅拌区组织为马氏体和贝氏体的混合组织。接头显微硬度结果显示,搅拌区的硬度明显高于母材,搅拌区与母材之间存在一个软化区。旋转速度为400 r/min时,接头抗拉强度最高,达到1 070MPa,为母材的99%,基本等同于母材的抗拉强度;接头的断后伸长率为11. 2%,达到母材的50%。旋转速度为200 r/min时,接头断裂于搅拌区,其他旋转速度下接头均断裂于软化区,断裂于软化区的断口形貌呈现韧性断裂特征。     

水下搅拌摩擦焊对铝/铜接头组织与性能的影响

目的 采用搅拌摩擦焊,对比分析大气环境和水下环境下铝/铜接头的组织与性能,以期获得力学性能更优异的铝/铜焊接接头。方法 利用搅拌摩擦焊,在焊接速度为40 mm/min、旋转速度为1 000 r/min的条件下,分别在大气环境和水下环境下对厚度为9 mm的6061铝合金板和T2纯铜板进行焊接。然后,对铝/铜界面、焊核区进行扫描电镜及能谱分析,并对铝/铜界面及焊核区进行物相分析,确定产物相组成。最后,对铝/铜试样进行拉伸及硬度检测。结果 铝/铜接头均无裂纹、气孔等缺陷。铜颗粒弥散分布在焊核区,铝/铜界面形成金属间化合物层。水下搅拌摩擦焊下界面元素扩散距离明显变短,且金属间化合物厚度更薄。铝/铜接头的金属间化合物为AlCu和Al4Cu9。大气环境焊接下接头的抗拉强度为130.6 MPa,断裂方式为脆性断裂;水下焊接下接头的抗拉强度为199.5 MPa,断裂方式为韧性断裂。水下环境下的接头硬度值更高,其中热影响区的硬度最低值约为65HV。结论 水下搅拌摩擦焊铝/铜接头无裂纹、气孔等缺陷。组织上,水下搅拌摩擦焊的铝/铜接头界面元素扩散距离更短,硬脆的金属间化合物更少;性能上,水下搅拌摩擦焊的铝/铜接头强度更高,抗拉强度达到199.5 MPa,达到母材的74.4%。     

转速对铝铜异种材料水下搅拌摩擦焊接接头组织与性能的影响

采用水下搅拌摩擦焊接(submerged friction stir welding,SFSW)技术对2024-T4铝合金和紫铜进行连接,研究转速对接头微观组织与力学性能的影响。结果表明:接头成型良好,无裂纹、孔洞等缺陷。随转速升高,接头表面平整度提高,大量铜被卷入焊核区(nugget zone,NZ),NZ组织结构逐渐混乱。SFSW过程中,冷却水有效抑制了晶粒粗化和脆性金属间化合物生成。当转速为750r/min时,接头抗拉强度为227MPa,达到铜母材的70.3%,随转速增大,接头的抗拉强度和伸长率降低。     

316L不锈钢薄板焊缝成形及力学性能研究

目的 减少1 mm厚度316L不锈钢薄板在焊接生产过程中出现的缺陷等问题,并提高不锈钢薄板焊缝成形质量和焊接接头力学性能。方法 采用脉冲激光焊接技术实现对厚度1 mm的316L不锈钢薄板的精确焊接,并利用金相显微镜、维氏硬度计、万能拉伸试验机和扫描电镜对焊缝的表面形貌、微观结构、力学性能、断口形貌进行表征分析。结果 当激光功率为403 W、输出电流为150 A、焊接速度为150 mm/min、离焦量为−5.525 mm时,焊缝正反面的形貌规则无缺陷。焊缝区内的微观结构主要由δ-铁素体和奥氏体2种晶粒构成,相较于母材及热影响区,焊缝区晶粒尺寸更细小均匀,平均硬度为156HV,表现出更高的硬度特性。焊接接头的抗拉强度和屈服强度均值分别达到643.28 MPa和305.95 MPa,相对于母材的强度分别提高了7%和49%;平均断后伸长率为37.2%,达到原始母材伸长率的55%;断裂呈现韧性断裂的塑性变形和延展性特征。结论 优化调整焊接工艺参数后,1 mm厚度316L不锈钢薄板的焊缝成形质量提高,无缺陷且微观组织分布均匀,焊接接头强度显著提高。     

2219铝合金TIG和FSW接头力学及疲劳性能

目的 研究钨极氩弧焊(TIG)和搅拌摩擦焊(FSW)对2219铝合金(母材)力学及疲劳性能的影响。方法 通过拉伸试验,得到了母材、TIG和FSW接头的抗拉强度和伸长率;通过疲劳性能试验测试了母材、TIG和FSW接头在不同应力下相应的疲劳寿命,根据疲劳试验结果绘制了其试样的S-N曲线;使用扫描电子显微镜观察并分析了疲劳断口的形貌特征。结果 未焊接的铝合金母材抗拉强度和伸长率最高,分别为506 MPa和15.92%;TIG接头抗拉强度和伸长率分别为330 MPa和7.65%,FSW接头抗拉强度和伸长率分别为310 MPa和8.74%。母材、TIG和FSW接头等3种疲劳试样在2×10⁶次循环下的疲劳强度分别为129、108、115 MPa,其疲劳断口均可分为裂纹源区、裂纹扩展区和瞬间断裂区,疲劳裂纹分别起始于试样表面的局部变形区、第二相夹杂物和“吻接”缺陷。疲劳裂纹扩展区的主要形貌为疲劳辉纹和二次裂纹,瞬间断裂区以脆性断裂为主。结论 TIG和FSW等2种焊接工艺均导致了2219铝合金的强度、塑韧性和疲劳性能降低,其接头表面的第二相夹杂物和“吻接”缺陷促进了疲劳裂纹的萌生。     

Microstructure and failure mechanisms of refill friction stir spot welded 7075-T6 aluminum alloy joints

In this paper, the microstructure and mechanical properties of 7075-T6 aluminum alloy joints joined by refill friction stir spot welding (RFSSW) were investigated. The keyhole was refilled successfully, and the microstructure of the weld exhibited variations in the grain sizes in the width and the thickness directions. There existed defects (hook, voids, bonding ligament, etc.) associated to the material flow in the weld. Mechanical properties of the joint have been investigated in terms of hardness and tensile/shear and cross-tension test, and the fracture mechanisms were observed by SEM (scanning electron microscope). The hardness profile of the weld exhibited a W-shaped appearance in the macroscopic level, which reached the minimum at the boundary of the sleeve and the clamping ring. The variation laws between tensile/shear and cross-tension strength and processing parameters were rather complicated. The void in the weld played an important role in determining the strength of the joint. On the whole, the preferable strength can be obtained at lower rotational speed. Shear fracture mode was observed under tensile–shear loadings, and nugget debonding, plug type fracture (on the upper sheet) and plug type fracture (on the lower sheet) modes were observed under cross-tension loadings. It was also observed that the main feature affecting the mechanical properties of the joint is the alclad between the upper and lower sheets and the connecting qualities between the stir zone and thermo-mechanically affected zone.     

汽车高强钢SG1000激光复合焊接力学性能研究

目的 针对汽车高强钢SG1000焊接接头恶化等问题,研究了SG1000激光复合焊接的力学性能。方法 选用等强匹配焊丝MG90-G对高强钢SG1000进行激光复合焊接,对焊接接头进行拉伸和低温冲击韧性试验,并结合扫描和硬度监测等手段对焊缝组织和断口形貌进行分析。结果 由于激光的预热作用,高强钢SG1000激光复合焊接成形件的焊缝美观,焊接过程稳定可靠,焊接熔池深度较大,有效改善了传统焊接的咬边、飞溅、气孔等缺陷。焊缝组织主要由板条马氏体和奥氏体晶粒组成,热影响区的过热区内部板条马氏体和奥氏体晶粒比较粗大,而焊接母材主要为细小的板条马氏体和奥氏体晶粒。焊接拉伸断口主要为细小且较浅的韧窝,且韧窝底部存在第二相粒子及夹杂物,焊接拉伸断口断裂于热影响区且微观形貌为韧性断裂;冲击微观形貌主要由准解理小平面及河流花样组成,且存在一定数量大小不一的韧窝交错分布,焊接冲击断口断裂于热影响区且微观形貌也为韧性断裂。结论 焊缝热影响区的晶粒比非热影响区的晶粒粗大,拉伸和冲击断裂均发生于热影响区;随着激光功率的增大,复合焊接接头的力学性能呈现逐渐增强的趋势;随着焊接速度的增大,复合焊接接头的力学性能呈现先增强后削弱的趋势。高强钢SG1000激光复合焊接最佳工艺参数如下:激光功率为9.5 kW,焊接速度为0.8 m/min,对应屈服强度为1 072 MPa,抗拉强度为1 175 MPa,断裂伸长率为13.5%,冲击断裂吸收的能量为30.8 J、焊缝中心显微硬度为342 HV。     

铝合金薄板搭接高速 FSW 缺陷及断裂行为

目的 为了拓展搅拌摩擦焊技术应用,对薄板搭接结构高速搅拌摩擦焊工艺优化与工程应用提供 借鉴与指导。方法 采用圆锥无螺纹搅拌针,进行了 6061 铝合金薄板搭接高速搅拌摩擦焊接,对接头界 面缺陷及其断裂模式进行分析,探讨了转速对 6061 铝合金薄板搭接接头成形及性能的影响规律。结果 发现在无螺纹圆锥搅拌针、高转速（6000~9000 r/min）条件下,接头塑性金属在后退侧易形成飞边流出, 导致下板前进侧出现孔洞缺陷,且随转速增大,界面缺陷尺寸逐渐增大,当转速达到 10 000 r/min 时, 孔洞尺寸有所减小,此时接头拉剪强度最高,为 123 MPa。对试样拉剪断裂位置分析发现,高速搭接接 头断裂位置主要有两种,分别断裂在结合界面处或在前进侧下板,且转速在 9000 r/min 以上越趋向于在 结合界面断裂。结论 高转速搭接焊接必须协调轴肩相貌、焊接工装约束等条件,保证接头塑性金属充 分流动而不流失,才能获得成形良好无缺陷的接头。     

薄板铝铜搭接搅拌摩擦焊工艺

目的研究铝铜异种材料的搅拌摩擦焊搭接工艺,揭示搭接接头界面行为演变的基本规律。方法对1mm的6061铝合金与1 mm的紫铜薄板进行搅拌摩擦焊搭接焊接,测试焊缝的力学性能,对焊缝组织进行分析。结果焊缝表面成形良好,焊缝内部无缺陷。接头的最高拉伸强度达到1447 N,观察拉伸接头断口形貌,发现断裂均发生在上层铝合金的热影响区。结论接头连接界面区域生成钩状"自锁紧"结构,这种钩状"自锁紧"结构增加了铝铜之间的有效接触面积,有利于提高焊缝连接强度。     

Microstructure and mechanical properties of friction spot welded 6061-T4 aluminum alloy

Friction spot welding (FSpW) is a relatively new solid state joining technology developed by GKSS. In the present study, FSpW was applied to join the 6061-T4 aluminum alloy sheet with 2 mm thickness. The microstructure of the weld can be classified into four regions, which are stir zone (SZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and the base material (BM), respectively. Meanwhile, defects such as bonding ligament, hook and voids are found in the weld, which are associated to the material flow. The hardness profile of the weld exhibits a W-shaped appearance and the minimum hardness is measured at the boundary of TMAZ and SZ. Both the tensile/shear strength and cross-tension strength reach the maximum of 7117.0 N and 4555.4 N at the welding condition of the rotational speed of 1500 rpm and duration time of 4 s. Compared to cross-tension strength, the tensile/shear strength were stable with the variation of processing parameters. Three different fracture modes are observed under tensile/shear loading, which are plug type fracture, shear fracture and plug-shear fracture. There are also there different fracture modes under cross-tension loading, which are plug type fracture (on the upper sheet), nugget debonding and plug type fracture (on the lower sheet).     

Study on cold metal transfer welding–brazing of titanium to copper

3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti₂Cu, TiCu and AlCu₂Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface.     

Microstructure characterization and properties of carbon steel to stainless steel dissimilar metal joint made by friction welding

Dissimilar metals of 1045 carbon steel and 304 stainless steel are joined successfully by friction welding. The microstructure variation and mechanical properties are studied in detail. The weld interface can be clearly identified in central zone, while the two metals interlock with each other by the mechanical mixing in peripheral zone. On carbon steel side, a thin proeutectoid ferrite layer forms along weld interface. On stainless steel side, austenite grains are refined to submicron scale. The δ-ferrite existing in stainless steel decreases from base metal to weld interface and disappears near the weld interface. Severe plastic deformation plays a predominant role in rapid dissolution of δ-ferrite compared with the high temperature. Carbide layer consisting of CrC and Cr₂₃C₆ forms at weld interface because of element diffusion. Metastable phase CrC is retained at room temperature due to the highly non-equilibrium process and high cooling rate in friction welding. The fracture appearance shows dimple fracture mode in central zone and quasi-cleavage fracture mode in peripheral zone. Further analysis indicates that welding parameters govern tensile properties of the joint through influencing the thickness of carbide layer at weld interface and heterogeneous microstructure in thermo-mechanically affected zone on carbon steel side.     

Fabricating Defect-Free API X65 Steel Welds under Underwater Wet Conditions using Friction Taper Plug Welding

The experiment on API X65 steel was carried out using friction taper plug welding (FTPW) under underwater wet conditions at room temperature. Sound weld formation can be achieved vastly at axial force ranging from 25 to 40 kN and a rotating speed of 7000 rpm. The microstructure of the weld zone consists of lath martensite, upper bainite, granular bainite, polygonal ferrite, and acicular ferrite. The microstructure of heat affected zone (HAZ) mainly consists of lath bainite as well as a bit of lath martensite and granular bainite. The tensile properties of defect-free welds are excellent. The maximum impact energy of the V-notch of bonding area can reach 110 J, which was conducted at 0°C with an error of ±12.5 J. The typical SEM impact fracture morphology presents areas of cleavage, quasi-cleavage, and dimples.     

Q960E超高强钢焊接接头组织和性能研究

目的 对Q960E超高强钢的焊接工艺进行研究以获得高强高韧的焊接接头。方法 选择超高强钢Q960E作为母材、FK1000ER120S–G焊丝作为填充材料进行MAG焊,采用改变焊接电流的方式来研究焊接热输入对焊接接头组织和性能的影响。结果 当焊接电流为155～230 A时,均获得了全焊透无明显缺陷的焊缝。随着焊接热输入的增大,焊接接头中各亚区宽度增大,其中焊缝区变化最为显著,在最小热输入条件下焊缝宽度为3.98 mm,在最大热输入条件下焊缝宽度增至5.53 mm。对焊接接头进行组织分析发现,焊缝组织主要为针状铁素体和板条马氏体;完全相变区组织主要为板条马氏体;未完全相变区组织主要为回火马氏体和部分重结晶形成的马氏体。硬度测试表明,在热影响区的回火区发生了软化现象,最低硬度仅为290HV;在完全相变区发生了硬化现象,硬度最大值可达500HV。在不同热输入条件下,焊接接头各亚区硬度变化趋势一致,焊接接头抗拉强度为995～1 076 MPa,拉伸试验均断裂在热影响区,断后伸长率为9.33%～10.21%,断裂时存在颈缩现象,为韧性断裂。随着热输入的增加,粗晶区马氏体板条束宽度增大,未完全相变区...     

Experimental study of friction taper plug welding for low alloy structure steel: Welding process,defects, microstructures and mechanical properties

A research investigation has been undertaken to identify the various stages and variation of welding parameters in friction taper plug welding (FTPW) process and to explore their effects on the performance and properties of the welds. According to the variation of axial force, the overall FTPW process is divided into feeding phase, pressing phase, welding phase, and forging phase. The rotating speed, welding force, and burn-off rate remain nearly constant in welding phase. However, the torque peaks in welding phase when after few seconds of welding force setting is reached. Rising the welding force would increase the peak torque, welding torque, and burn-off rate, but decrease the welding time. When improper welding parameter is used lack of bonding and incomplete filling defects would form within the weld. The microstructure of the weld metal is consist of retained austenite, pearlite, and various Widmanstätten ferrite. In heat affect zone, it is mainly of lathy upper bainite. Defect free welds exhibit favorable tensile properties of which 548.3 MPa tensile strength and 27.5% elongation that equal to the base metal could be found.