Comparison of 2A12 aluminium alloy joint by ultrasonic assisted friction stir welding and friction stir welding

Ultrasonic assisted friction stir welding （UAFSW） is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, 2A12 aluminum alloy was welded by this process and conventional, respectively. The tensile tests, microstructure and fracture surface of FSW joint and UAFSW joint were analyzed. The research results show that the surface forming texture of ultrasonic assisted friction stir welding joint, compared with conventional, is finer and more uniform, showing metallic matte color. The grains are much finer in weld nugget zone, thermo-mechanically affected zone and heat-affected zone; S-phase particles size is much smaller and distribution is more homogeneous in the matrix. The tensile strength of UAFSW joint is 94. 13% of base metal, and the elongation is 11.77%. The tensile strength of FSW joint is 83.15% of base metal, and the elongation is 8.81%. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints.     

Friction stir welding of AZ31 magnesium alloy

Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.     

Microstructure and mechanical properties of the joint of 6061 aluminum alloy by plasma-MIG hybrid welding

Plasma-MIG (metal inert gas arc welding) hybrid welding of 6061 aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out.The microstructures and mechanical properties of the welded joint were investigated by optical microscopy,X-ray diffraction (XRD),energy dispersive spectroscopy (EDS),tensile test,hardness test and scanning electron microscope (SEM) were used to judge the type of tensile fracture.The results showed that the tensile strength of welded joint was 142 MPa which was 53.6％ of the strength of the base metal.The welding seam zone was characterized by dendritic structure.In the fusion zone,the columnar grains existed at one side of the welding seam.The fibrous organization was found in the base metal,and also in the heat affected zone (HAZ) where the recrystallization occurred.The HAZ was the weakest position of the welded joint due to the coarsening of Mg2Si phase.The type of tensile fracture was ductile fracture.     

Comparative Analysis on Microstructure and Mechanical Properties between EBW and TANDEM Welding of 7A52 Aluminum Alloy Joint

The plates with 20mm thickness of 7A52 aluminum alloy were welded by electron beam welding and TANDEM welding with ER5356 filler,respectively.The microstructure and mechanical properties of the joints were investigated.The results showed that the microstructure of EBW metal was finer and tighter than TANDEM welding.The heat-affected zone of the EBW joint was narrower,its hardness was higher and the tensile strength improved obviously compared to TANDEM welding.Excellent quality control of the EBW joint was made without abnormal porosity,inclusions and micro-cracks.Therefore,the EBW joint of 7A52 aluminum alloy showed excellent performance.     

Effect of the heat input on microstructure and properties of submerged arc welded joint of 08Cr19MnNi3Cu2N stainless steel

SAW308L submerged arc welding wire and SJ601A submerged arc welding flux were selected to weld the 12 mm 08Cr19MnNi3Cu2N low nickel and high nitrogen austenitic stainless steel plates with three different welding heat input, and microstructure,tensile properties, microhardness and corrosion properties of the welded joints were studied. The results show that no defects are found in the three groups of welded joints, and the welded joints have better performance.The tensile strength of 08Cr19MnNi3Cu2N stainless steel welded joints with different heat input is slightly lower than that of the base metal,and fracture occurs in the weld zone, and the hardness of the weld zone is lower than that of the base metal. The weld microstructure of stainless steel welded joints with different heat input is composed of austenite + δ ferrite, and ferrite is uniformly distributed in austenite. With the increase of the welding heat input, the ferrite content in the weld zone decrease gradually, the grain size in the thermal affected zone increase gradually, and the impact toughness reduce.     

Microstructure and mechanical properties of wrought magnesium alloy AZ31B welded by laser-TIG hybrid

The laser-TIG hybrid welding was mainly used to weld the wrought magnesium alloy AZ31B. The tech-nical characteristics of laser-TIG hybrid welding process was investigated and the interactional mechanism between laser and arc was discussed, at the same time the microstructure and mechanical properties of the wrought magnesi-um alloy AZ31B using laser-TIG hybrid welding were analyzed by optical microscope, EPMA, SEM, tensile ma-chine, hardness machine. The experimental results show that the presence of laser beam boosts up the stability of the arc during high speed welding and augments the penetration of weld； the crystal grains of magnesium alloy weld are fine without porosity and cracks in the best welding criterion and the microstructure of HAZ does not become coarse obviously. The elements profile analysis reveals that Mg content in the weld is lower than that of the base metal, but Al content is higher slightly. Under this experimental condition, the wrought magnesium alloy AZ31B joint can be achieved using laser-TIG hybrid process and the tensile strength of the joint is equivalent to that of the base metal.     

Texture and mechanical properties of metal inert gas welded 6082-T651 aluminum alloy joints

Metal inert gas(MIG) welding was conducted with 12 mm thick 6082-T651 aluminum alloy plate to investigate the microstructure and mechanical properties of welded joint. The microstructure and element distribution of weld seam were characterized by electron backscattered diffraction(EBSD) and electron probe microanalysis(EPMA). The weld seam has typical cube texture({001}100) characteristics. The closer to the center of weld seam, the weaker the texture feature, the higher the proportion of high-angle grain boundaries. The average tensile strength of joint was 232 MPa which is up to 72% of 6082 aluminum alloy base metal, and the bending angle for the root bend test sample reached 90° without cracks. The lack of strengthening phase and the existence of welding pores and inclusions in the weld seam caused the degradation of mechanical properties of resultant joint. The microhardness increased from the weld center to the base metal,but the overaging zone caused by welding thermal cycle was softening part of the joint, which had lower hardness than the weld seam.     

Microstructure and Strain Hardening of a Friction Stir Welded High-Strength Al–Zn–Mg Alloy

Microstructural evolution and strain hardening behavior of a friction stir welded（FSWed） high-strength7075Al-T651 alloy were evaluated.The nugget zone was observed to consist of fine and equiaxed recrystallized grains with a low dislocation density and free of original precipitates,but containing uniformly distributed dispersoids.The strength,joint efficiency,and ductility of the FSWed joints increased with increasing welding speed.A joint efficiency of ＊91% was achieved at a welding speed of 400 mm/min and rotational rate of 800 r/min,while the ductility remained basically the same as that of the base metal.There was no obvious strain rate sensitivity observed in both base metal and welded joints.While both the base metal and FSWed joints exhibited stage III and IV hardening characteristics,the hardening capacity,strain hardening exponent,and strain hardening rate all increased after friction stir welding.     

工业纯钛光纤激光-MIG复合焊接工艺及性能

采用光纤激光与熔化极惰性气体保护电弧焊(MIG焊)复合焊接工业纯钛,分别对激光焊、MIG焊和复合焊接头的焊缝表面成形、横断面进行了观察,并进行了激光焊和复合焊接头的拉伸试验及杯突试验.结果表明,复合焊的电弧稳定性比MIG焊显著提高,焊接速度可提高7倍;复合焊与激光焊接头的抗拉强度高于母材;复合焊接头的杯突值优于激光焊接头的杯突值,这是因为复合焊焊缝的微观组织有利于接头的塑性.因此,采用光纤激光-MIG电弧复合焊接方法很好地实现了工业纯钛的高速焊接,焊缝成形良好,接头的塑性优于单一激光焊的塑性.

Abstract：

Fiber laser-metal inert gas (MIG) arc hybrid welding was used to weld the commercial pure titanium (CP-Ti). The weld appearance, cross section, tensile strength, Erichsen value and microstructure of the CP-Ti welded joints were studied. The results show that the arc stability is substantially improved and the welding speed can be increased to 7 times by fiber laser-MIG hybrid welding. The welded joints by laser welding and the hybrid welding exhibit the higher ultimate tensile strength than those of the base metal. In addition, the welded joint by the fiber laser-MIG hybrid welding has higher Erichsen values than that by laser joints. The difference in plasticity is attributed to the microstructure changes in the welded joint of hybrid welding. Thus, the fiber laser-MIG hybrid welding of CP-Ti can be carried out suecessfully at higher welding speed with a good combination of weld bead appearance and plasticity.     

Ti17合金惯性摩擦焊接头力学性能与组织分析

通过室温拉伸、高温拉伸试验以及金相分析对 Ti17 合金惯性摩擦焊接接头的显微组织和力学性能进行了研究.结果表明,采用惯性摩擦焊焊接 Ti17 合金可获得室温及高温性能良好的焊接接头,其焊接接头的室温及高温抗拉强度都不低于母材;Ti17合金母材组织为α+β相,并且β相呈针状均匀分布在α相的基体上;不同焊接工艺参数对 Ti17 合金惯性摩擦焊接头热影响区和焊缝的组织没有影响,其热影响区组织为α+β相,并且β相呈针状均匀分布在α相的基体上,与母材组织相同,焊缝组织为细小的等轴晶.

Abstract：

The microstructures and properties of Ti17 alloy joints welded by inertia friction welding (IFW) were investigated by room-temperature tensile test, high-temperature tensile test and metallographic analyses. The results show that the joint with good performance at room and high temperature for Ti17 alloy can be obtained in IFW. Both the tensile strengths of welded joints at room temperature and at high temperamre are not less than those of the base metal. The microstructure of Ti17 alloy is α+β phase, and the needle β phase is distributing on the α phase. While welding, different welding parameters can not affect the microstructures of the HAZ and the weld seam. The microstructure of HAZ is the same as that of the base metal, and that of the welded seam is fine equiaxed crystal.     

镁合金小孔变极性等离子弧缝焊工艺

采用小孔变极性等离子弧缝焊工艺实现了AZ31B镁合金板材的连接,得到了高质量的焊接接头,焊后利用光学显微镜、万能拉伸试验机和显微硬度仪等设备对焊接接头的组织与性能进行了检测分析.结果表明,小孔变极性等离子弧缝焊工艺可以在不开坡口、不需背面强制成形保护的条件下,实现单面施焊双面获得良好的成形;焊接接头的热影响区不明显,平均拉伸剪切力能达到7.3 kN以上;焊缝区组织均匀,晶粒细小,硬度值均高于母材;是一种理想的提高镁合金焊接效率和质量的方法.     

Incoloy 825镍基高温合金电子束焊工艺及接头组织与力学性能分析

采用电子束焊，对空冷器管箱Incoloy 825镍基高温合金进行对接焊试验. 通过对焊接接头的组织观察，并结合拉伸力学性能以及接头的冲击韧性等试验，分析镍基高温合金电子束焊接头的组织和力学性能. 结果表明, 采用电子束焊焊接镍基高温合金可以得到良好的焊接接头，焊缝区组织由大片等轴晶和少量柱状晶组成；焊缝区没有出现明显的元素烧损现象；焊缝、热影响区硬度达到母材硬度值；焊缝接头抗拉强度达到600 MPa，接近母材抗拉强度，接头断裂形式为韧性断裂；焊缝和热影响区的冲击吸收能量高于母材区，其中焊缝区的冲击吸收能量达到了262 J，冲击断口形貌为韧窝状.     

基于Incoloy800H钨极氩弧焊接头组织及其性能分析

在2 mm厚800H合金钨极氩弧焊试验的基础上,研究焊接接头的微观组织和析出相成分,并分析焊接接头的力学性能和抗晶间腐蚀性能,观察拉伸断口和晶间腐蚀试样的形貌。结果表明:焊缝组织为柱状晶和等轴晶,热影响区晶粒明显长大,焊接接头中有少量的TiN和富Cr相(Fe,Cr)_(23)C_6析出相存在;母材、热影响区和焊缝的HV硬度分别为1730、1526和1590 MPa;室温抗拉强度和延伸率分别为565.0 MPa、31.8%,均超过ASME标准关于800H合金规定值(450.0 MPa和30.0%),拉伸断裂为韧性断裂;焊接接头高温(650℃)抗拉强度和延伸率分别为394.5 MPa、15.5%,其断口是混合型断口;较接头组织,母材腐蚀更为严重,表面晶界开裂并伴有少量且尺寸较小的腐蚀坑,基体中TiN缺陷处易引起点蚀。     

1420铝锂合金双光点激光焊接头组织性能

在2mm厚1420铝锂合金双光点激光焊接试验的基础上,研究接头的组织与性能。对比分析单、双光点激光焊接头各区域的组织、显微硬度及室温拉伸力学性能,并观察断口形貌。结果表明:1420铝锂合金双光点激光焊接头组织与单光点激光焊接头组织分布类似,从熔合区至焊缝中心依次是等轴细晶、柱状晶和等轴树枝晶,但较单光点接头细化;双光点激光焊接头各区域硬度低于母材,但高于单光点激光焊接头;双光点激光焊接头焊态抗拉强度较母材下降,但略高于单激光焊接头,可达母材的86%。     

TC4厚壁管全位置PAW工艺及接头性能分析

介绍了一种适合TC4钛合金厚壁管的等离子弧焊接新工艺,通过对工艺参数分区控制和优化匹配,实现了钛合金管道全位置优质焊接.采用光学显微镜、扫描电镜以及显微维氏硬度仪分别对特征位置焊接接头的显微组织、断口形貌以及显微硬度进行表征.结果表明,特征位置接头焊缝区及热影响区显微组织均主要由网篮状α'相、针状α相以及粗大β相组成;接头拉伸性能良好,拉伸试样均断裂于母材处;冲击试样的断裂形式为韧性断裂;焊缝区及热影响区硬化区的硬度值高于母材.     

新型9Cr-1Mo钢搅拌摩擦焊接头组织及性能

采用钨铼合金搅拌工具对新型9Cr-1Mo钢进行搅拌摩擦焊工艺试验,探讨焊缝成形、组织及性能变化规律. 结果表明,在300和400 r/min的转速,50 mm/min的焊接速度下可获得无缺陷接头;焊缝主要由搅拌区和热力影响区组成,具有明显的马氏体淬硬组织特征;高温热影响区为淬硬马氏体和回火马氏体混合组织,低温热影响区为过回火马氏体组织. 焊缝区具有晶粒细化特征,其晶粒尺寸约为母材69.2%. 焊缝区产生明显硬化,最高硬度约为母材硬度值的2.0倍. 焊接接头抗拉强度达到母材98%以上,搅拌区和热影响区冲击吸收能量分别达到母材的77.8%和87.4%,表明搅拌摩擦焊接头仍具有较好强韧匹配.     

AZ61A镁合金等离子焊接头组织与性能

通过拉伸、硬度、弯曲试验和金相组织分析,研究AZ61A镁合金等离子焊接头的拉伸性能、硬度、弯曲性能和金相显微组织。结果表明,拉伸试件的断裂处均位于焊缝区,抗拉强度值分别为220MPa和223MPa,且Rm(W)/Rm(pm)0.7,满足试验要求;所有弯曲试件均未出现断裂,弯曲性能良好;等离子焊所获得的接头热影响区窄且晶粒粗大,焊缝区晶粒细小,组织由α相及其上弥散分布着的灰色点状物Mg17Al12组成;焊缝区整体硬度高于热影响区和母材,热影响区基本未发生软化。     

填充焊丝对6A02铝合金光纤激光焊接接头组织性能的影响

采用ER4043焊丝开展了1.0 mm厚6A02铝合金的光纤激光填丝焊接,对比分析了是否填丝对焊缝横截面形貌、接头组织、显微硬度分布和拉伸性能的影响.结果表明,激光填丝焊缝成形饱满,能够显著提高焊前装配的最大间隙容忍裕度.与自熔激光焊接接头相比,激光填丝焊接接头熔合区附近的柱状晶组织和焊缝中心的混合组织（柱状晶+等轴晶）均相对粗化,接头软化现象更加明显,焊态时接头抗拉强度基本相当,仅达到母材水平的83.2%,但经历固溶时效热处理后,接头强度得以恢复,并高于母材水平,断后伸长率获得显著改善,可以达到21.29%,远高于前者的8.13%.     

AZ91D镁合金TIG焊接接头组织及性能研究

使用与母材AZ91D镁合金同质焊丝进行TIG焊接.采用金相显微镜、X射线衍射仪、拉伸试验机、布氏硬度计等分析测试手段对接头的组织特征、相组成和力学性能进行分析.结果表明:焊接电流为140 A,氩气流量12 L/min时,焊接接头的抗拉强度为母材的80%左右,断裂发生在热影响区.焊缝区组织是比母材晶粒细小、更均匀的等轴晶.X射线衍射表明该区由α-Mg固溶体和Mg17Al12相组成.