铝合金搅拌摩擦焊工艺参数库的建立

搅拌摩擦焊(FSW)作为一种新型焊接技术,由于其与传统的熔化焊相比具有焊接缺陷少、无须填充材料及保护气体、焊接前无须复杂的处理工作、能量消耗少等特点而得到广泛应用。但其焊接参数往往由操作者凭经验给出,带有一定的盲目性。本文首先针对FSW工艺进行了一般性研究,找到其规律性,并建立了其焊接参数数据库。数据库系统采用大型SQL Server 2000数据库为平台,建立了材料库、工艺库、刀具库和产品库等,具有查询、维护和浏览等功能。该数据库的建立为FSW工艺的推广应用和工艺管理系统的研究奠定了基础。

铝合金搅拌摩擦焊电主轴冷却系统的设计与仿真

铝合金搅拌摩擦焊电主轴作为铝合金搅拌摩擦焊机床的核心部件,其热态稳定性影响着机床的高质量的焊接。为有效预测并控制铝合金搅拌摩擦焊电主轴运转过程中的热态性能及其对铝合金搅拌摩擦焊主轴焊接质量的影响,建立铝合金搅拌摩擦焊电主轴水路的热态分析有限元模型,分析热稳定状态下铝合金搅拌摩擦焊电主轴水路的温度场分布以及冷却系统对铝合金搅拌摩擦焊电主轴温升的影响,分析结果表明,提高铝合金搅拌摩擦焊电主轴现有冷却系统的冷却效率可有效控制主轴电机和内置轴承的温升;同时,仿真分析冷却水路对铝合金搅拌摩擦焊电主轴温升的影响,揭示铝合金搅拌摩擦焊电主轴温度场分布的非线性特征。进行合理的轴承配置、选择合适冷却水道尺寸以及增加冷却水流量均可有效改善电主轴热态性能。

基于轮廓法测试铝合金搅拌摩擦焊内部残余应力

采用轮廓法测试8 mm厚AA6061-T6铝合金搅拌摩擦焊接头的内部纵向残余应力。详细介绍了轮廓法的测试过程,获得了搅拌摩擦焊接头切割面上的纵向残余应力分布全貌,分析了残余应力沿厚度变化特征。研究结果表明,轮廓法能够获得搅拌摩擦焊接头的内部应力分布,测试的搅拌摩擦焊接头纵向残余应力沿横向方向为不太明显的M形分布;在焊接区域前进侧的纵向应力大于后退侧应力,纵向残余应力沿厚度分布不均匀,峰值纵向拉应力为168 MPa,约为母材室温屈服强度的60%,且峰值拉应力出现在焊接接头前进侧边缘距上表面5 mm(62.5%厚度)位置。

一种复合式铝合金搅拌摩擦焊主轴的结构设计

对铝合金搅拌摩擦焊主轴的现状进行了简要介绍,结合铝合金搅拌摩擦焊存在的不足及今后的发展趋势,在分析研究主轴关键结构的基础上,考虑目前现有铝合金搅拌摩擦焊主轴的结构,设计一种新型的复合式铝合金搅拌摩擦焊主轴。此复合式铝合金搅拌摩擦焊主轴设计有中空气冷和散热筋结构,可较好地解决搅拌摩擦焊接过程存在的主轴冷却散热密封、锁紧搅拌头快速更换等问题,通过气腔压力调节、齿条键槽结构和直线轴承结构实现主轴回抽滑移,实现铝合金搅拌摩擦焊主轴点焊的功能,消除焊接遗留的匙孔。

铝合金搅拌摩擦焊电主轴的结构设计与分析

对铝合金搅拌摩擦焊技术和电主轴技术进行了简要介绍,结合目前铝合金搅拌摩擦焊实际焊接过程中存在的不足及今后的发展趋势,在分析研究电主轴单元关键技术的基础上,设计研发一种新型的中空冷却自动调节负荷铝合金搅拌摩擦焊专用电主轴,较好地解决了铝合金搅拌摩擦焊接过程存在的主轴长时间工作出现的温升高、转轴承载负荷过大和搅拌头损坏后不能及时更换等问题,实现了主轴持续焊接冷却散热及时、拌头快速更换、转轴承载自动调整。经国家检测机构鉴定,达到设计标准。

轨道车辆铝合金搅拌摩擦焊质量保证及控制标准分析

现行轨道车辆领域主要焊接标准为EN 15085:2007,该标准发布时搅拌摩擦焊工艺方法尚未在轨道车辆焊接国际认证企业中大量应用。EN 15085:2007仅提及允许铝合金材料使用该方法,再无其它信息。在标准缺位的情况下,仅应用EN 15085不能完全实现轨道车辆铝合金搅拌摩擦焊的焊接质量保证及控制,其需要综合应用“EN 15085系列标准”、“ISO 3834系列标准”、“欧洲轨道车辆焊接委员会指南-第二部分”、“ISO 25239系列标准”及“项目技术规范的补充说明”等。以轨道车辆某项目铝合金搅拌摩擦焊为例,解析其焊接质量保证及控制标准应用,并结合工程实例技术规范及常见问题补充说明若干内容。

新能源车电池壳用铝合金搅拌摩擦焊研究

为了研究新能源车电池壳用铝合金搅拌摩擦焊的焊接性能,进行6060铝合金搅拌摩擦焊接试验,并且焊后进行力学性能分析及显微观察,得出结论:搅拌针转速1500r/min、逬给速度500 mm/min时,6060铝合金焊缝抗拉强度可达母材强度79%,焊缝硬度高于母材硬度,并且焊缝表面成形良好,焊缝内部无缺陷,为实际生产过程中电池壳用铝合金的选用提供参考。

铜-铝合金搅拌摩擦焊研究进展

搅拌摩擦焊是一种固相连接技术,可消除铜-铝异种金属常规焊接时产生的焊接缺陷,提升焊接质量,丰富了铜-铝异种金属的焊接方法,进而促进了铜-铝金属在工业中的应用。从工艺因素、微观组织以及力学性能等方面介绍铜-铝异种合金搅拌摩擦焊近年来的研究进展,并对未来发展进行了展望。

6082-T6铝合金双面搅拌摩擦焊焊接接头组织及性能

对6082-T6铝合金搅拌摩擦焊焊缝的组织和力学性能进行研究,采用搅拌摩擦焊(FSW)对厚度为30 mm的6082-T6铝合金进行双面对接焊,焊后沿板厚方向每隔4 mm切割试样,切割为7层,研究由焊缝表层至底部性能的变化.结果表明,焊缝整体的抗拉强度为199. 34 MPa,为母材的64. 3%,伸长率为7. 8%;第1层到第7层抗拉强度依次为203. 13、194. 20、182. 73、169. 40、179. 15、191. 58、202. 07 MPa;正面焊缝焊核区纵向0~15 mm的显微硬度分布为下降趋势,与之相同反面焊缝焊核区纵向0~15 mm的显微硬度分布也呈现下降趋势.上部轴肩产生的摩擦热自上到下不断降低,是造成中下部工件性能下降的主要原因.

Microstructure and mechanical properties of dissimilar Al-Cu joints by friction stir welding

Dissimilar friction stir welding between 1060 aluminum alloy and annealed pure copper sheet with a thickness of 3 mm was investigated. Sound weld was obtained at a rotational speed of 1050 r/min and a welding speed of 30 mm/min. Intercalation structure formed at the crown and Cu/weld nugget （WN） area promotes interracial diffusion and metallurgical bonding of aluminum and copper. However, corrosion morphology reveals the weak bonding mechanism of internal interface, which causes the joint failing across the interface with a brittle-ductile mixed fracture mode. The tensile strength of the joint is 148 MPa, which is higher than that of the aluminum matrix. Crystal defects and grain refinement by severely plastic deformation during friction stir welding facilitate short circuit diffusion and thus accelerate the formation of A14Cu9 and A12Cu intermetallic compounds （IMCs）. XRD results show that A14Cu9 is mainly in Cu/WN transition zone. The high dislocation density and formation of dislocation loops are the major reasons of hardness increase in the WN.

Effect of welding heat input and post-welded heat treatment on hardness of stir zone for friction stir-welded 2024-T3 aluminum alloy

The microstructure and hardness of the stir zone （SZ） with different welding heat inputs were investigated for friction stir-welded 2024-T3 aluminum by transmission electron microscopy, differential scanning calorimeter and Vickers micro-hardness test. The results show that welding heat input has a significant effect on the hardness of the SZ. Under high welding heat input condition, a higher welding speed is beneficial for improving the hardness of the SZ. However, when the welding heat input is low, the hardness of the SZ elevates with increasing the rotation speed. The hardness of the SZ decreases after post-welded heat treatment due to overaging. The joints welded at 500 r/min and 100 mm/min show a high resistance to overaging. The reduction of hardness in the SZ is only 3.8%, while in other joints, the reduction is more than 10%. The morphology of strengthening precipitates plays important roles for the improvement of hardness.

Numerical studies of effect of tool sizes and pin shapes on friction stir welding of AA2024-T3 alloy

Coupled thermo-mechanical model was used to investigate the effects of the pin diameter, the shoulder diameter and the in conical angle on the heat generations, the material deformations and the energy histories in friction stir welding（FSW） of AA2024-T3 alloy. Results indicate that the shoulder-plate contact area takes more important contribution to the heat generation than the pin-plate contact area. The increase of the shoulder diameter or the decrease of the pin diameter can lead to the increase of the welding temperature in FSW, but the change of shoulder size is more important. Compared to the cases in FSW of AA6061-T6, the input power is obviously increased in FSW of AA2024-T3 and the ratio of the plastic dissipation to the friction dissipation becomes decreased.

Visualization and simulation of plastic material flow in friction stir welding of 2024 aluminium alloy plates

Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visualized material flow patterns, a three-dimensional model was developed to conduct the numerical simulation of the temperature profile and plastic material flow in friction stir welding. The calculated velocity contour of plastic flow in close proximity of the tool is generally consistent with the visualized results. As the tool rotation speed increases at a constant tool travel speed, the material flow near the pin gets stronger. The predicted shape and size of the weld nugget zone match with the experimentally measured ones.

Thermal modeling of underwater friction stir welding of high strength aluminum alloy

The thermal modeling of underwater friction stir welding （FSW） was conddcted with a three-dimensional heat transfer model. The vaporizing characteristics of water were analyzed to illuminate the boundary conditions of underwater FSW. Temperature dependent properties of the material were considered for the modeling. FSW experiments were carried out to validate the calculated results, and the calculated results showed good agreement with the experimental results. The results indicate that the maximum peak temperature of underwater joint is significantly lower than that of normal joint, although the surface heat flux of shoulder during the underwater FSW is higher than that during normal FSW. For underwater joint, the high-temperature distributing area is dramatically narrowed and the welding thermal cycles in different zones are effectively controlled in contrast to the normal joint.

Microstructure evolution along thickness in double-side friction stir welded 7085 Al alloy

The microstructure evolution in the weld zone of double-side friction stir welded（DS-FSWed） 7085-T7452 Al alloy was investigated by the electron backscatter diffraction method.The results indicate that DS-FSW process results in substantial grain refinement.The misorientation angle distribution shows a very high volume fraction of high angle grain boundary（HAGB）（above 75%） under DS-FSW condition at rotational rate of 300 r/min.The fraction of HAGB rapidly decreases with increasing the rotational rate from 300 to 950 r/min,and the obvious growth of grain in the weld nugget zone（WNZ） is presented.The average grain sizes in the elongated grains of thermal-mechanical affected zone（TMAZ） and partially equiaxed and coarser grains of thermal affected zone（HAZ） are 7.3 and 15.7 μm with the fractions of HAGBs less than 43% and 30%,respectively.The intensities of（100）,（110） and（111） pole figures in the WNZ obviously decrease when compared with those in the BM and present significantly difference along the thickness direction of plate.

Effect of corrosive environment on fatigue property and crack propagation behavior of Al 2024 friction stir weld

In this investigation, 2024 aluminium alloy plates were friction stir welded, a sequence of experiments was performedincluding fatigue and crack propagation tests in air, under pre-corrosion and in a 3.5% NaCl solution, in combination withfractography analyses of near-threshold region, Paris region and finial fracture region with the aid of scanning electron microscopy（SEM）. Results showed that the corrosive environment caused a dramatical decrease in fatigue lives of FS welds, the corrosionfatigue lives of FS welds were almost a half of those of the as-welded specimens. The crack growth rates in FS welds were higherthan their counterparts in base materials, under the corrosive environment, the crack growth rate differences between base materialsand FS welds become increasingly apparent with the increase of stress intensity factor range ΔK, but the pre-corrosion process hadlittle effect on the FS welds’ crack propagation behavior except for shortening the crack initiation lives greatly.

Parametric optimization of friction stir welding parameters of marine grade aluminium alloy using response surface methodology

Friction stir welding between AA5052-H32aluminium plates is performed by central composite design technique of response surface methodology.It is found that the welding parameters such as tool pin profile,tool rotational speed,welding speed,and tool tilt angle play a major role in deciding the joint characteristics.The joints fabricated using tapered square pin profile tool with a tool rotational speed of600r/min,welding speed of65mm/min,and tool tilt angle of1.5°result in an unexpected weld efficiency of93.51%.Mathematical models are developed to map the correlation between the parameters and responses(ultimate tensile strength and elongation)and these models are optimized to maximize the ultimate tensile strength of the friction stir welded joint.Response plots generated from the mathematical models are used to interpret the interaction effects of the welding parameters on the response variables.Adequacy of the developed models is validated using analysis of variance(ANOVA)technique.Results from the confirmatory experiments plotted in scatter diagram show a good agreement with predicted models.Different grain structures in various zones of the weld are examined by observing the micro and macro structures of the weld.

Influence of FSW parameters on formation quality and mechanical properties of Al 2024-T351 butt welded joints

The influence of R/v ratio on joint quality in 2024-T351 aluminum alloy was studied. Specimens were subjected to friction stir welding with the rotation rates of 750, 950 and 1180 r/min and welding speed between 73 and 190 mm/min, providing R/v ratio between 5.00 and 10.27. The welded joints were tested by means of both non-destructive （visual, penetrant and X-ray inspection） and destructive （metallographic, tension and hardness） testing. In all specimens typical zones are revealed, with corresponding differences in grain size. Tensile efficiency of the joints obtained is in the range of 52.2%to 82.3%. The results show that the best quality is obtained at R/v ratio of 8.06, 10.17 and 10.27. This behavior is attributed to the assumption that the material flows around the pin with an optimal speed, i.e. sufficient amount of material is available to fill the gap and prevent tunnel formation. R/v ratio also showed influence on hardness distribution, onion features and crack initiation/propagation zones.

Numerical simulation of friction stir butt-welding of 6061 aluminum alloy

A two-dimensional computational fluid dynamics model was established to simulate the friction stir butt-welding of 6061 aluminum alloy. The dynamic mesh method was applied in this model to make the tool move forward and rotate in a manner similar to a real tool, and the calculated volumetric source of energy was loaded to establish a similar thermal environment to that used in the experiment. Besides, a small piece of zinc stock was embedded into the workpiece as a trace element. Temperature fields and vector plots were determined using a finite volume method, which was indirectly verified by traditional metallography. The simulation result indicated that the temperature distribution was asymmetric but had a similar tendency on the two sides of the welding line. The maximum temperature on the advancing side was approximately 10 K higher than that on the retreating side. Furthermore, the precise process of material flow behavior in combination with streamtraces was demonstrated by contour maps of the phases. Under the shearing force and forward extrusion pressure, material located in front of the tool tended to move along the tangent direction of the rotating tool. Notably, three whirlpools formed under a special pressure environment around the tool, resulting in a uniform composition distribution.

Optimization of process parameters to maximize ultimate tensile strength of friction stir welded dissimilar aluminum alloys using response surface methodology

Aluminium alloys generally present low weldability by traditional fusion welding process. Development of the friction stir welding （FSW） has provided an alternative improved way of producing aluminium joints in a faster and reliable manner. The quality of a weld joint is stalwartly influenced by process parameter used during welding. An approach to develop a mathematical model was studied for predicting and optimizing the process parameters of dissimilar aluminum alloy （AA6351 T6-AA5083 Hlll）joints by incorporating the FSW process parameters such as tool pin profile, tool rotational speed welding speed and axial force. The effects of the FSW process parameters on the ultimate tensile strength （UTS） of friction welded dissimilar joints were discussed. Optimization was carried out to maximize the UTS using response surface methodology （RSM） and the identified optimum FSW welding parameters were reported.