铝锂合金搅拌摩擦焊接热循环

搅拌摩擦焊接过程中，焊件上任一位置于搅拌头行走到该位置所在垂直于焊缝直线的瞬间，热循环温度达到最大值，并随着搅拌头远离而迅速降低。焊缝起点受搅拌头扎入行为的影响，而焊缝终点受搅拌头提起行为的影响，二者经受的热循环温度低于焊缝其它部位。然而焊缝起点和终点间的材料经受稳定的热循环作用。焊缝中心经受的焊接热循环温度最高，为415℃。焊缝两侧材料经受不同的热循环作用，前进侧略高于后退侧7～12℃。     

Friction Stir Lap Welding of Magnesium Alloy to Steel: A Preliminary Investigation

An initial study was made to evaluate the feasibility of joining magnesium alloy AZ31 sheet to galvanized steel sheet in a lap configuration using friction stir welding (FSW). Two different automotive sheet steels were used for comparative evaluation of the dissimilar joining potential: a 0.8 mm thick, electrogalvanized (EG) mild steel, and a 1.5 mm thick hot-dipped galvanized (HDG) high-strength, low-alloy (HSLA) steel. These steels were joined to 2.33 mm thick AZ31B magnesium sheet. A single FSW tool design was used for both dissimilar welds, and the process parameters were kept the same. The average peak load for the AZ31-1.5 mm steel weld joint in lap shear mode was found to be 6.3 ± 1.0 kN. For the AZ31-0.8 mm steel weld, joint strength was 5.1 ± 1.5 kN. Microstructural investigation indicates melting of the Zn coating present on the steel sheets, and subsequent alloying with the Mg sheet resulted in the formation of a solidified Zn-Mg alloy layer.     

6061铝合金搅拌摩擦焊接头组织与性能研究

采用搅拌摩擦焊方法(FSW)对6 mm厚的6061-T4铝合金板材进行对接,焊后利用光学显微镜(OM)和扫描电镜(SEM)分析、对比了焊接接头和母材的显微组织和断口形貌特征,并测试了其室温拉伸性能和显微硬度。实验结果表明:选择了适合于6061-T4铝合金板材搅拌摩擦焊的工艺参数:焊接时搅拌头旋转速度为1200 r.min-1,工件的进给速度为300 mm.min-1,在此参数下获得了与母材等强度、韧性接近于母材的焊接接头,为此种合金应用于汽车关键零部件提供了可靠的工艺方法。FSW板材接头焊核区的组织和性能明显优于其他区,热影响区是接头最薄弱的部分,焊核区的硬度最高,而热影响区的硬度最低,焊缝金属发生回复再结晶使晶粒细化。断口分析表明,断裂发生在热影响区,由于搅拌头的旋转运动和热量的累积,该区存在晶粒长大、组织粗化现象。对工艺参数的优化实验表明,搅拌头旋转速度与焊接速度对接头性能的影响存在一定的适配关系,通过工艺参数的调整可以有效地控制热影响区的焊缝组织和改善焊接接头的性能。细晶强化是搅拌摩擦焊接头强度与韧性提高的主要原因。     

Grain Structure Development During Friction Stir Welding of Single-Crystal Austenitic Stainless Steel

The high-resolution electron backscatter diffraction (EBSD) technique was used to study the grain boundary development and texture evolution during friction stir welding (FSW) in a single-crystal austenitic stainless steel. Strain-induced crystal rotations were found to be induced by simple shear deformation. With the crystal rotations, the single-crystal structure was broken up into a fine-grained polycrystalline aggregate in the stir zone. This process was deduced to be governed by continuous and discontinuous recrystallizations operating during the FSW process. The final texture which evolved in the stir zone was dominated by $ A/\bar{A}\left\{ {111} \right\} \, \langle 110 \rangle $ ideal simple shear orientations.     

Effect of Process Parameters on Microstructure and Mechanical Properties in Friction Stir Welding of Aluminum Alloy

Friction stir welding process is a promising solid state joining process with the potential to join low melting point materials, particularly aluminum alloys. The most attractive reason for this is the avoidance of solidification defects formed during conventional fusion welding processes. Tool rotational speed and the welding speed play a major role in deciding the weld quality. In the present work an effort has been made to study the effect of the tool rotational speed and welding speed on mechanical and metallurgical properties of friction stir welded joints of aluminum alloy AA6082-T651. The micro hardness profiles obtained on welded zone indicate uniform distribution of grains in the stir zone. The maximum tensile strength obtained is 263 MPa which is about 85% of that of base metal. Scanning electron microscope was used to show the fractured surfaces of tensile tested specimens.     

镁合金搅拌摩擦焊接技术

对5mm厚镁合金AZ31B板材的摩擦焊接技术进行了试验研究，结果表明：适合其板材的搅拌摩擦焊接的搅拌头，材料为W6MoSCr4V2高速钢，结构为凹面圆台形，根部直径5．5mm，端部直径为2．5mm，轴肩尺寸为12mm，长度为4．7mm。镁合金搅拌摩擦焊接头的抗拉强度可达母材的90％，延伸率可达母材的50％。搅拌摩擦焊接头焊合区为动态再结晶组织，在接头前进边焊合区与母材有明显的分界线，返回边过渡区有金属微熔的迹象。     

Corrosion at the Weld Nugget of the Friction-Stir-Welded Medium Strength Steel: Effect of Microstructure

Metallurgical and Materials Transactions A - In the present investigation, friction stir welding (FSW) was carried out on C-Mn steel using various welding parameters. The microstructural...     

搅拌摩擦焊用钨铼合金的研究进展

搅拌摩擦焊接技术是一种环保、低成本的固相连接技术,已经在航空航天、轨道交通和新能源汽车等领域得到广泛应用。对于高熔点合金材料如钛合金和不锈钢的搅拌摩擦焊接而言,搅拌头材料成了主要制约因素。钨铼（W-Re）合金凭借其高熔点、高硬度和强抗腐蚀性等优点,已成为研究和应用最热的搅拌摩擦焊接高熔点合金的搅拌头材料。本文综述了近年来在搅拌摩擦焊工艺中以W-Re合金作为搅拌头材料的制备方法、复合强化技术和应用场景的研究进展。此外,还展望了拓宽W-Re合金在搅拌摩擦焊领域应用的前景,包括降低W-Re合金的生产成本和提高其服役寿命等方面,旨在推动W-Re合金搅拌头材料在搅拌摩擦焊领域的进一步应用和发展。     

Microstructural Evolution During Friction Stir Welding of Mild Steel and Ni-Based Alloy 625

Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW.     

Microstructure of the Joint of 1565chM Alloy Sheets Fabricated by Friction Stir Welding

The microstructure in the joints of a non-heat-treatable aluminum–magnesium 1565chM alloy sheets fabricated by friction stir welding is studied. The structure near the interface between the base metal and a welded joint is examined. Friction stir welding results in a gradient structure with ultrafine grains at the center of the welded joint. The structure in the welded joint forms by the mechanism resulting in the formation of a layered ultrafine structure due to plastic deformation by shear and rotation of structural fragments. Layers are assumed to form due to the balance between the strain hardening and the softening caused by frictional heating and heat released during deformation. An analogy between the microstructure in the joint fabricated by friction stir welding and the microstructure formed by sliding friction is drawn.     

Dissimilar Friction Stir Welding of Carbon Steel and Stainless Steel: Some Observation on Microstructural Evolution and Stress Corrosion Cracking Performance

Specimens of carbon steel (CS) and stainless steel (SS) 316 was joined together by double sided butt joint Friction Stir Welding method. Effect of the tool rotational speed and specimen preheat temperature on resultant microstructure and mechanical behavior was studied. Constant traveling speed of 100 mm/min, tool rotational speed of 500 and 1000 rpm in combination with preheat temperature of 50 and 100 °C was employed for this study. No sign of root crack was observed in all specimens. Optical microscopy identified four distinct zones characterized as the stir zone, thermal mechanically affected zone (TMAZ) in both SS and CS specimen, and heat affected zone (HAZ) in CS specimen. No HAZ in SS was observed. Scanning electron microscopy revealed formation of a thin void layer on several locations at the boundary between the TMAZ and the re-oriented region of SS side, while on the CS side no voids were identified. The grain size on the TMAZ of CS was observed to be smaller compared to the HAZ region. No sign of root crack was observed in all specimens. The specimens were subjected to U bend. Specimens joined with 1000 rpm rotational speed developed a brittle behavior and failed in U bend test. The extent of the crack and brittleness was proportional to the applied preheat. U bent specimens from 500 rpm rotation demonstrated a good stress corrosion cracking behavior in 30,000 ppm solution of sodium chloride (NaCl).     

Effect of Arc Welding Processes on the Weld Attributes of Type 316LN Stainless Steel Weld joint

The present study aims at understanding the effect of various arc welding processes on the evolution of microstructure, mechanical properties, residual stresses and distortion in 9 mm thick type 316LN austenitic stainless steel weld joints. Weld joints of type 316LN stainless steel were fabricated by three different arc welding processes which were commonly employed in the nuclear industry. All the weld joints passed radiographic examination. Microstructural characterization was done using optical and scanning electron microscope. Volume fraction of δ-ferrite was lowest in the A-TIG weld joint. The A-TIG welded joint exhibited adequate strength and maximum impact toughness values in comparison to that of weld joints made by SMAW and FCAW processes. The A-TIG weld joint was found to exhibit lowest residual stresses and distortion compared to that of other welding processes. This was attributed to lower weld metal volume and hence reduced shrinkage in the A-TIG weld joint compared to that of weld joints made by FCAW and SMAW processes which involved v-groove with filler metal addition. Therefore, type 316LN stainless steel A-TIG weld joint consisting of lower δ-ferrite, adequate strength, high impact toughness, lower residual stresses and distortion was suited better for elevated temperature service compared to that of SMAW and FCAW weld joints.     

A Transient Thermal Model for Friction Stir Weld. Part II: Effects of Weld Conditions

In Part II of this series of articles, the transient thermal model, which was introduced in Part I, is used to explore the effects of welding conditions on the heat generation and temperature. FSW of the 6061-T651 aluminum alloy is modeled to demonstrate the model. The following two steps are adopted to study the influence of welding conditions on the heat generation and temperature. First, the thermal model is used to compute the heat generation and temperature for different welding conditions, the calculated results are compared with the reported experimental temperature, and a good agreement is observed. Second, the analytical method is used to explore the approximate functions describing the effect of welding conditions on the heat generation and temperature. Based on the computed results, we discuss the relationship between the welding conditions, heat generation, temperature, and friction coefficient, and propose a relationship map between them for the first time at the end.     

Interfacial Reaction during Friction Stir Welding of Al and Cu

Commercially pure copper was joined to a 1050 aluminum alloy by friction stir welding. A specific configuration where the tool pin was fully located in the aluminum plate was chosen. In such a situation, there is no mechanical mixing between the two materials, but frictional heating gives rise to a significant thermally activated interdiffusion at the copper/aluminum interface. This gives rise to the formation of defect-free joints where the bonding is achieved by a very thin intermetallic layer at the Cu/Al interface. Nanoscaled grains within this bonding layer were characterized using transmission electron microscopy (TEM). Two phases were identified, namely, Al₂Cu and Al₄Cu₉ phases. The nucleation and growth of these two phases are discussed and compared to the standard reactive interdiffusion reactions between Cu and Al.     

Friction Stir Welding of Dissimilar Al/Al and Al/Non-Al Alloys: A Review

Metallurgical and Materials Transactions B - Friction stir welding is a solid-state welding technique that has many advantages over traditional fusion welding, and has been widely adopted in the...     

Friction Stir Welding in HSLA-65 Steel: Part I. Influence of Weld Speed and Tool Material on Microstructural Development

A systematic set of single-pass full penetration friction stir bead-on-plate and butt-welds in HSLA-65 steel were produced using a range of different traverse speeds (50 to 500?mm/min) and two tool materials (W-Re and PCBN). Microstructural analysis of the welds was carried out using optical microscopy, and hardness variations were also mapped across the weld-plate cross sections. The maximum and minimum hardnesses were found to be dependent upon both welding traverse speed and tool material. A maximum hardness of 323?Hv(10) was observed in the mixed martensite/bainite/ferrite microstructure of the weld nugget for a welding traverse speed of 200?mm/min using a PCBN tool. A minimum hardness of 179?Hv(10) was found in the outer heat-affected zone (OHAZ) for welding traverse speed of 50?mm/min using a PCBN tool. The distance from the weld centerline to the OHAZ increased with decreasing weld speed due to the greater heat input into the weld. Likewise for similar energy inputs, the size of the transformed zone and the OHAZ increased on moving from a W-Re tool to a PCBN tool probably due to the poorer thermal conductivity of the PCBN tool. The associated residual stresses are reported in Part II of this series of articles.