Microstructure and XRD analysis of FSW joints for copper T2/aluminium 5A06 dissimilar materials

Copper (T2) and aluminium alloy (5A06) were welded by friction stir welding (FSW). The microstructure, mechanical properties and phase constituents of FSW joints were studied by metallography, tensile testing machine and X-ray diffraction. The results indicated that the high quality weld joint could be obtained when tool rotational speed is 950 rpm, and travel speed is 150 mm/min. The maximum value of tensile strength is about 296 MPa. The metal Cu and Al close to copper side in the weld nugget (WN) zone showed a lamellar alternating structure characteristic. However, a mixed structure characteristic of Cu and Al existed in the aluminium side of weld nugget (WN) zone. There were no new Cu-Al intermetallic compounds in the weld nugget zone.     

Achieving ultra-high strength friction stir welded joints of high nitrogen stainless steel by forced water cooling

The microstructure and properties of water-cooled and air-cooled friction stir welded (FSW) ultra-high strength high nitrogen stainless steel joints were comparatively studied. With additional rapid cooling by flowing water, the peak temperature and duration at elevated temperature during FSW were significantly reduced. Compared to those in the air-cooled joint, nugget zone with finer grains (900 nm) and heat affected zone with higher dislocation density were successfully obtained in the water-cooled joint, leading to significantly improved mechanical properties. The wear of the welding tool was significantly reduced with water cooling, resulting in better corrosion resistance during the immersion corrosion test.     

5083铝合金搅拌摩擦焊接头的显微组织与力学性能

对8 mm厚5083-H321铝合金板进行了搅拌摩擦焊接试验,研究了焊接工艺参数对搅拌摩擦焊接头显微组织和力学性能的影响。结果表明:该搅拌摩擦焊接头焊核区显微组织为细小的等轴晶组织,热机影响区为拉伸弯曲变形组织,热影响区非常窄,其晶粒尺寸与母材相当;综合接头表面形貌和拉伸性能得到较佳的搅拌摩擦焊接工艺参数为使用搅拌针为三棱形带螺纹、轴肩为内扣型的搅拌头,主轴转速为300 r·min^-1,焊接速率为120 mm·min^-1;在该工艺条件下接头表面成形良好,抗拉强度可达到母材的94.5%。     

Microstructural evolution and mechanical properties of friction stir welded joint of Fe–Cr–Mn–Mo–N austenite stainless steel

2 mm thick Fe–18.4Cr–15.8Mn–2.1Mo–0.66N high nitrogen austenite stainless steel plate was successfully joined by friction stir welding (FSW) at 800 rpm and 100 mm/min. FSW did not result in the loss of nitrogen in the nugget zone. The arc-shaped band structure, consisting of a small amount of discontinuous ferrite aligning in the bands and fine austenite grains, was a prominent microstructure feature in the nugget zone. The discontinuous ferrite resulted from newly formed ferrite during welding and the remained ferrite, whereas the fine austenite grains were formed due to dynamic recrystallization of the initial austenite during FSW. The fine dynamically recrystallized grains in the nugget zone significantly increased the hardness compared to that of the base material. The strength of the joint was similar to that of the base material, with the joint failing in the base material zone.     

氧化膜对6082铝合金搅拌摩擦焊接头疲劳性能的影响

对6 mm厚的6082-T6铝合金进行两种表面处理然后实施搅拌摩擦焊接,研究了对接面氧化膜对接头组织和疲劳性能的影响。结果表明,进行速度为1000 mm/min的高速焊接时,对接面未打磨和打磨的接头焊接质量都良好,接头强度系数达到81%;两种接头的疲劳性能基本相同,疲劳强度均为100 MPa;少数样品在焊核区外断裂,大部分样品在热影响区断裂。与接头相比,两种接头焊核区的疲劳性能有所提高,均为110 MPa,在疲劳测试中裂纹并未沿“S”线萌生和扩展。     

Residual stress distribution and microstructure in the friction stir weld of 7075 aluminum alloy

In order to study the relationship between residual stress (RS) and the microstructure of friction stir weld (FSW), RS profiles through thickness in the un-welded aluminum alloy 7075 plate and in middle layer of its FSW joint were determined nondestructively by the short-wavelength X-ray diffraction (SWXRD) and neutron diffraction. Microstructure and mechanical properties of the FSW joint were also studied by optical microscopic analysis, and microhardness and tensile strength measurements. RS profiles measured by the two methods had the same distribution trend. The maximum tensile RS tested by SWXRD and neutron diffraction in transverse and longitudinal direction occurred in the weld nugget. Microhardness in the direction perpendicular to the weld line showed a “W” shape distribution. Position of the local maximal extremum of RS in thermo-mechanically affected zone corresponded to that of minimal microhardness. The grain-refined strengthening caused by the recrystallization in the weld nugget kept the joint from fracturing at this region notwithstanding the maximum tensile RS. And the tensile fracture occurred near the boundary of welding zone and thermo-mechanically affected zone where minimum of hardness and maximum of RS appear at the same position.     

5083铝合金搅拌摩擦焊接头拉伸行为研究

目的 研究5083铝合金搅拌摩擦焊接（FSW）的组织、力学性能和拉伸应变,分析接头的拉伸行为。方法 采用数码相机、光学显微镜、电子扫描显微镜等表征分析方法,对焊缝的表面宏观成形、微观组织、断口形貌进行分析;利用拉伸机、三维数字动态散斑应变测量分析系统和显微维氏硬度计对接头的力学性能和拉伸应变进行测试。结果 不同焊接工艺参数下FSW接头的最低抗拉强度为305 MPa,断后延伸率达到了14%以上;焊核区拉伸应变沿板厚方向呈现上高下低和上宽下窄的不均匀梯度分布,发生了较大程度的变形强化,直到拉伸应力达到抗拉强度。断裂失效前300/120接头的最大拉伸应变在晶粒粗大的母材区,500/120和500/200接头的最大拉伸应变则位于晶粒尺寸差异较大的后退侧焊核区与热力影响区交界处。接头拉伸断口宏观上均为45°剪切韧性断裂,微观上均以韧窝韧性断裂为主,而高热输入500/120接头出现脆性断裂特征,其延伸率明显降低。结论 高热力耦合输入使铝合金FSW接头薄弱区发生转变,强韧性降低。     

Effect of welding parameters on microstructure and mechanical properties of friction stir welded joints of AA7039 aluminum alloy

A high strength Al–Zn–Mg alloy AA7039 was friction stir welded by varying welding and rotary speed of the tool in order to investigate the effect of varying welding parameters on microstructure and mechanical properties. The friction stir welding (FSW) process parameters have great influence on heat input per unit length of weld, hence on temperature profile which in turn governs the microstructure and mechanical properties of welded joints. There exits an optimum combination of welding and rotary speed to produce a sound and defect free joint with microstructure that yields maximum mechanical properties. The mechanical properties increase with decreasing welding speed/ increasing rotary speed i.e. with increasing heat input per unit length of welded joint. The high heat input joints fractured from heat affected zone (HAZ) adjacent to thermo-mechanically affected zone (TMAZ) on advancing side while low heat input joints fractured from weld nugget along zigzag line on advancing side.     

Material stirring during FSW of Al–Cu: Effect of pin profile

Friction stir welding (FSW) joins the material in solid state, and it gets evolved as a new and effective technique to join dissimilar materials such as aluminum and copper. FSW tool design and configuration critically affect the joint quality. This study has evaluated the effect of different pin profiles used during FSW of AA5754 Al alloy and commercially pure copper in a butt configuration on the microstructure, material movement, and microhardness for the different joints. The joining is performed through the different pin profiles of cylindrical, taper, cylindrical cam, taper cam, and square shape at the rotational and welding speed of 900?rpm and 40?mm/min respectively. Among all joints, the square pin profile provides good joining and microhardness. Square tool pin profile facilitates good amount of mixing at nugget zone, which consequently increases the hardness. The material movement in square tool pin profile joint is also studied on the longitudinal plane to understand the effect of pulsating and stirring action on the material mixing pattern in dissimilar FSW. It is evident that the softer material in the stir zone gets more stirring, and the flow lines are clearly visible for the stirred material.     

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%。     

Friction stir welding of carbon nanotubes reinforced Al-Cu-Mg alloy composite plates

Carbon nanotubes(CNTs) reinforced Al-Cu-Mg composite plates of 2.2 mm in thickness after extrusion and T4 treatment were joined by friction stir welding(FSW) and the joint efficiency reaches 87%. There was no precipitate in both heat-affected zone(HAZ) and nugget zone(NZ) as a medium rotation rate of 800 rpm and a relative high travel speed of 100 mm min-1were used. In the NZ, FSW disarranged the alignment of CNTs to random orientation and dispersed CNT uniformly. The orientation of CNTs perpendicular to the tensile direction and the possible dissolution of solute clusters made the HAZ become the weakest zone in the joint leading to the failure in the HAZ.     

焊接速度对 7A52 铝合金 FSW 组织及力学性能的影响

目的在保证搅拌速度一定时,针对8 mm厚的7A52铝合金,在不同焊接速度下采用搅拌摩擦焊(FSW)进行焊接试验,研究其焊接接头的显微组织及力学性能。方法利用搅拌摩擦焊机进行对接焊接,焊后制取金相试样观察焊接接头宏观形貌和显微组织,并测定其力学性能。结果7A52铝合金FSW焊接接头焊核区的面积随着焊接速度的增大而增大,当焊接速度为250mm/min时,焊接接头的焊核区面积最大,焊核区的显微组织都为细小的等轴晶,焊接接头横截面的焊核区呈明显"洋葱环"的形貌,而热力影响区的结构特征则呈现出了较高的塑性变形流线层。焊接接头显微硬度分布都呈现出"W"形变化,在焊接速度为150 mm/min时,焊接接头的平均抗拉强度能达到452 MPa,达到了母材抗拉强度的89%。结论通过对不同焊接速度下7A52铝合金FSW焊接接头的组织和性能进行研究,得到了不同焊接速度下焊接接头组织和力学性能。     

6005A铝合金挤压型材搅拌摩擦焊接头的疲劳性能

对6005A-T6铝合金挤压型材进行焊速为1000 mm/min的搅拌摩擦高焊速焊接,研究了对接面机械打磨对接头组织和力学性能的影响.结果 表明,与生产中常用的焊前打磨处理相比,尽管对接面未机械打磨的接头焊核区的"S"线更明显,但是两种接头的硬度分布和拉伸性能相当,拉伸时都在最低硬度区即热影响区断裂.高周疲劳实验结果表...     

The microstructure and mechanical properties of friction stir welded Al–Zn–Mg alloy in as welded and heat treated conditions

High strength aluminium alloys generally present low weldability because of the poor solidification microstructure, porosity in the fusion zone and loss in mechanical properties when welded by fusion welding processes which otherwise can be welded successfully by comparatively newly developed process called friction stir welding (FSW). This paper presents the effect of post weld heat treatment (T₆) on the microstructure and mechanical properties of friction stir welded 7039 aluminium alloy. It was observed that the thermo-mechanically affected zone (TMAZ) showed coarser grains than that of nugget zone but lower than that of heat affected zone (HAZ). The decrease in yield strength of welds is more serious than decrease in ultimate tensile strength. As welded joint has highest joint efficiency (92.1%). Post weld heat treatment lowers yield strength, ultimate tensile strength but improves percentage elongation.     

转速对水下搅拌摩擦焊接7A04-T6铝合金组织与性能的影响

对7A04-T6铝合金板进行水下搅拌摩擦焊接(FSW),研究转速对水下FSW接头组织和力学性能的影响。结果表明:水下FSW接头的硬度最小值均位于热机械影响区。高转速条件下(950r/min)接头的硬度分布呈现"W"形,焊核区平均硬度值高于低转速条件下(475,600,750r/min)接头的硬度值。当焊速恒定为235mm/min,转速从475r/min提高到750r/min时,接头焊核区的析出相随转速的增大逐渐粗化,接头抗拉强度系数从89.71%降低到82.33%;当转速升高到950r/min时,析出相发生固溶时效,呈现细小弥散的分布特征,接头的强度系数提高到89.04%。接头具有较高的应变硬化能力,塑性伸长率较高。水下FSW接头的拉伸断口均呈现微孔聚合和解理混合断裂特征。     

Mechanical properties evolution during post-welding-heat treatments of double-lap Friction Stir Welded joints

The present study focuses on double-lap Friction Stir Welded (FSW) joints in 2024T3 and 7075T6 aluminium alloys subjected to several post-welding-heat treatments at warm (typical aging) and high temperature (solution range) followed by room temperature deformation (tensile tests). The effect of post-welding-heat treatments on the microstructure and mechanical properties of double lap FSW joints were investigated. Polarized Optical Microscopy (POM) and Scanning Electron Microscopy (SEM) analysis reveal a progressive change in grain size and morphology in high temperature post-welding-heat treated joints, leading to Abnormal Grain Growth in the stir zone. Stress–strain curves are rather flat for 200° and 300 °C post-welded heat treated joints while, for the other set of samples, stress increases with strain to reach maximum stress of 140–160 MPa. Micro-hardness profiles measured on transversal sections of post-welded heat treated joints reveal conditions (temperature and time) of hardness homogeneity at top, bottom and central nugget zone and/or along the whole measured profile. When homogeneity is reached, fracture occurs in the nugget. A relationship between hardness and tensile properties has been applied in the nugget.     

铝/钢异种金属的超声振动强化搅拌摩擦焊接工艺

采用新型超声振动强化搅拌摩擦焊接工艺实现了6061-T6铝合金以及QP980高强钢的搭接焊, 对比分析了有无超声作用下, 接头的宏观形貌、微观组织和拉伸剪切性能, 同时研究了超声振动对焊接载荷的影响。结果表明: 焊接前对母材施加超声振动, 可以起到软化母材的作用, 促进了材料的塑性流动, 扩大了铝/钢界面区和焊核区, 使更多的钢颗粒随搅拌针旋转进入铝合金侧, 在界面区边缘形成钩状结构, 进而提高了接头的失效载荷; 超声改变了FSW接头断裂位置和断口形貌, 提高了接头力学性能, 在本实验工艺参数范围内, 接头最大的平均失效载荷为4.99 kN; 当焊接速度为90 mm/min, 下压量为0.1 mm时, 施加超声振动使接头的平均失效载荷提高了0.98 kN, 拉剪性能提升28.24%;施加超声振动后轴向力F_z、搅拌头扭矩M_t和主轴输出功率分别下降2.46%, 6.44%和4.59%。     

Low cycle fatigue properties of friction stir welded joints of a semi-solid processed AZ91D magnesium alloy

A semi-solid processed (thixomolded) Mg–9Al–1Zn magnesium alloy (AZ91D) was subjected to friction stir welding (FSW), aiming at evaluating the weldability and fatigue property of the FSW joint. Microstructure analysis showed that a recystallized fine-grained microstructure was generated in the nugget zone (NZ) after FSW. The yield strength, ultimate tensile strength, and elongation of the FSW joint were obtained to be 192 MPa, 245 MPa, and 7.6%, respectively. Low-cycle fatigue tests showed that the FSW joint had a fatigue life fairly close to that of the BM, which could be well described by the Basquin and Coffin-Manson equations. Unlike the extruded magnesium alloys, the hysteresis loops of FSW joint of the thixomolded AZ91D alloy were basically symmetrical, while the non-linear or pseudoelastic behavior was still present. The FSW joint was observed to fail in the BM section rather than in the NZ. Fatigue crack initiated basically from the pores at or near the specimen surface, and crack propagation was mainly characterized by fatigue striations along with the presence of secondary cracks.     

Enhanced Mechanical Properties of Friction Stir Welded 5083Al-H19 Joints with Additional Water Cooling

3-mm-thick 5083Al-H19 rolled plates were friction stir welded(FSW) at tool rotation rates of 800 and200 rpm with and without additional water cooling. With decreasing the rotation rate and applying water cooling, softening in the FSW joint was significantly reduced. At a low rotation rate of 200 rpm with additional water cooling, almost no obvious softening was observed in the FSW joint, and therefore a FSW5083Al-H19 joint with nearly equal strength to the base material(BM) was obtained. Furthermore, the grains in the nugget zone were considerably refined with reducing the heat input and ultrafine equiaxed grains of about 800 nm were obtained in the lowest heat input condition. This work provides an effective method to achieve high property FSW joints of precipitate-hardened and work-hardened Al alloys.     

Microstructure and mechanical properties of friction stir welded joints made from ultrafine grained aluminium 1050

In order to obtain ultrafine grained structure, commercially pure aluminium (Al 1050) plates were subjected up to 8 passes of Incremental Equal Channel Angular Pressing (IECAP) following route C. Plates in different stages of IECAP were joined using Friction Stir Welding (FSW). All welded samples were investigated to determine their mechanical properties and structure evolution in the joint zone. The joining process reduced mechanical strength of material in the nugget zone, which was explained by the grain growth resulting from temperature rise during FSW. Nevertheless, the obtained results are promising in comparison to other methods of joining aluminium.