搅拌摩擦焊接Al-Li合金接头的微观组织及力学性能

采用锥形带螺纹搅拌头搅拌摩擦焊接5mm厚的Al—Li合金轧制板材，并对接头组织、力学性能及断裂特性进行了研究．结果表明，焊核区组织发生动态再结晶，形成细小的等轴晶晶粒，在等轴晶的晶界处析出大量的偏析相．热影响区组织发生回复和粗化反应，形成粗大的棒状回复晶粒；热机影响区组织发生弯曲变形，但整体上仍保留带状组织形貌，前进侧热机影响区组织变形程度高于后退侧，该区同时还发生回复反应，且后退侧热机影响区内的回复晶粒数量多于前进侧．拉伸实验结果表明，焊接速度v=40mm／min时，接头强度达到最大值，为345MPa；v=60mm／min时，接头延伸率达到最大值，为9．6％．硬度测试结果表明，搅拌摩擦焊接头发生软化，前进侧的软化区宽度大于后退侧．断口形貌分析表明，接头断裂模式为韧-脆混合型断裂．     

Structure-Property Correlation of AA2014 Friction Stir Welds: Role of Tool Pin Profile

The influence of rapid plastic deformation in the generation of welding heat during friction stir welding (FSW), supplementing the frictional heat generation by the tool shoulder, forms the thrust of the present investigation. Several researchers have highlighted the role of tool shoulder in the generation of frictional heat and suggested that the tool-material interface friction as the sole mechanism for heating. The configuration of tool pin profile is seldom studied for its contribution to welding heat through rapid plastic deformation at high strain rates (10³/s), especially while welding thick plates. An attempt has been made to understand the dependence of deformation heat generation with different tool pin profiles in welding 5 mm thick AA2014-T6 aluminum alloy, maintaining the same swept volume during the tool rotation. An attempt has also been made to correlate the influence of process response variables such as force and torque acting on the tool pin. To quantify the physical influence of tool pin profile, temperature measurements were made in the region adjacent to the rotating pin, close to nugget in the thermo-mechanically affected zone (TMAZ). It has been observed that the temperature rises at a relatively rapid rate in the case of hexagonal tool pin compared to the welds produced employing other tool pin profiles. It is observed that during FSW, extensive deformation experienced at the nugget zone and the evolved microstructure strongly influences the mechanical properties of the joint. The present study is also aimed at understanding the influence of tool profile on the microstructural changes and the associated mechanical properties. Transverse tensile samples failed at the nugget/TMAZ boundary due to localized softening. Hexagonal tool pin profile welds have shown higher tensile strength, low TMAZ width, and high nugget hardness compared to other tool pin profile welds.     

焊接速度对5754铝合金FSW接头微观组织和力学性能的影响

对3 mm厚的5754铝合金板材进行搅拌摩擦焊接，研究了搅拌头在转速800 r/min条件下，不同焊接速度(100 ~ 400 mm/min)对搅拌摩擦焊接头微观组织和力学性能的影响. 结果表明，5754铝合金FSW接头横截面形貌呈“盆”形. 随着焊接速度增加，5754铝合金FSW接头的焊核区和轴肩区的面积逐渐减小，而搅拌针区面积先增加后减小. 当焊接速度为300 mm/min时，搅拌针区面积达到最大值6.66 mm2，轴肩区和搅拌针区面积比例为0.97，5754铝合金FSW接头的强度系数达到97.5%，这主要是因为轴肩区和搅拌针区面积相近，增大了焊核区和热影响区界面面积，从而提高了FSW接头强度，拉伸断裂在焊核区以外(热影响区或基材区)，断口为韧性断口. 当焊接速度为400 mm/min时，5754铝合金FSW接头的强度系数为58.8%，拉伸试样均断裂在焊核区，断口为脆性断口.     

High-Speed Friction Stir Welding of T6-Treated B_4Cp/6061Al Composite

T6-treated 20 wt% B_4 Cp/6061 Al sheets were joined under welding speeds of 400–1200 mm/min by friction stir welding(FSW) with a threaded cermet pin. The macro-defect-free FSW joints could be achieved at high welding speeds up to 1200 mm/min, but larger plunge depth was required at the welding speeds of 800 and 1200 mm/min to eliminate the tunnel defect. In the nugget zone(NZ) of the joints, the B_4 C particles were broken up and uniformly redistributed. The NZ exhibited lower hardness than the base metal(BM), and the hardness value almost did not change with increasing welding speed, attributable to the dissolution of precipitates. Compared with the BM, the joints showed lower tensile strength. As the welding speed increased from 400 to 800 mm/min, the joint efficiencies were nearly the same and up to ～ 73%. When the welding speed increased up to 1200 mm/min, the tensile strength significantly decreased, due to the occurrence of kissing bond defect at the bottom of the NZ. With increasing welding speed, the fracture location of the joints transferred gradually from the heat-affected zone to the NZ due to the kissing bond defects.     

焊接参数对7A04铝合金搅拌摩擦焊接头组织与力学性能的影响

采用不同的焊接参数对3 mm厚7A04铝合金板进行焊接,并对接头的组织、沉淀相、力学性能及断口形貌进行了分析. 结果表明,焊核区组织发生动态再结晶,形成细小的等轴晶粒,热影响区晶粒发生明显粗化. TEM分析结果显示,经搅拌摩擦焊后,焊核区部分沉淀相溶解. 焊核区晶粒尺寸随焊接速度增大而减小. 当焊接速度为120 mm/min,旋转速度为800 r/min时,接头强度达到最大值 454.2 MPa,为母材的95%,断后伸长率为3.97%,为母材的70%. 硬度测试显示搅拌摩擦焊接头发生软化,焊缝区域硬度低于母材,硬度值最低点出现在热影响区;拉伸断口形貌SEM图像表明接头断裂方式为韧性和脆性混合型断裂.     

轴肩压入深度对AA2024/AA2024搅拌摩擦焊接头连接质量的影响

通过调节轴肩压入深度,研究了板厚3 mm的AA2024/AA2024搅拌摩擦焊接头连接质量的变化规律.结果表明,无轴肩压入深度时,AA2024/AA2024接头的搅拌针前进侧存在“隧道”缺陷；随着轴肩压入深度的增加,“隧道”缺陷逐渐消失,接头界面轴肩搅拌区出现氧化物夹杂缺陷(S线),并呈现先增后减的演化规律,在焊核区底部也出现S线,并呈现逐渐增大的分布规律；焊接速度100 mm/min,旋转频率为800 r/min,轴肩压入深度为0.2mm时,3 mm厚AA2024/AA2024对接接头抗拉强度达到370MPa,断面收缩率达到3.4％.     

A6N01-T5合金FSW和MIG焊接头疲劳裂纹扩展行为的对比

研究了6N01-T5铝合金搅拌摩擦焊(FSW)和氩弧焊(MIG)接头不同部位的疲劳裂纹扩展性能, 并对疲劳断口和接头组织进行了分析. 结果表明,对于FSW和MIG焊接头, 其裂纹扩展速率从高到低的部位依次为焊缝(核)区、热影响区和母材. 裂纹在FSW和MIG焊接头相同区域的扩展速率无明显差别, 然而裂纹在FSW接头细晶组织中开始扩展所需的门槛值ΔK要比对应的MIG焊接头高, 总体上其裂纹在FSW焊核区的抗疲劳裂纹扩展性能要优于对应的MIG焊缝区. 裂纹在FSW和MIG焊接头焊核(缝)区扩展的疲劳断口表现为脆性断裂, 而在热影响区则以规则和光滑的疲劳条纹形式扩展.     

7075铝合金搅拌摩擦焊接头变形及失效行为

使用搅拌摩擦焊（FSW）设备对厚度为6mm的7075高强度铝合金平板进行对接试验。设计出双径试样,采用液压伺服试验机对7075铝合金搅拌摩擦焊接头进行拉伸试验,并借助奥林巴斯显微镜和扫描电镜观察接头的变形及失效过程。结果表明,7075铝合金搅拌摩擦焊接头在拉伸过程中出现双颈缩现象,颈缩首先在后退侧出现,随着加载的进行,前进侧也出现颈缩现象。微裂纹在接头中的前进侧和后退侧颈缩区内晶界处由微孔洞聚集产生。随着应变的增加,微孔洞数量明显增加,当应变足够大时,微孔洞连接形成微裂纹。微裂纹沿着与加载方向成45°向焊核区进行扩展,导致接头断裂,断裂位置位于接头中的焊核区,断裂方式为剪切断裂混合着微孔聚集型断裂。     

Microstructure evolution and fracture behaviour of friction stir welded 6061-T6 thin plate joints under high rotational speed

6061-T6 sheets with 0.8?mm thickness were successfully welded using high-speed friction stir welding (FSW) technology. The microstructural evolution and fracture behaviour of the joints were studied. The results show that sound joints could be obtained at the investigated high rotational speed of 8000?rev?min^?1 and welding speeds of 300–1200?mm?min^?1. Compared with conventional rotational speed, the grain size in the nugget zone (NZ) is obviously refined under high rotational speed. The Mg₂Si, Al₈Fe₂Si and Al₂CuMg precipitates reprecipitated adequately in the NZ during high-speed FSW, resulting in the number of the precipitates increased significantly, and further alleviating the weld softening. The difference in weld softening leads to different fracture characteristics during the tensile process. After artificial aging, the maximum welding softening in all joints is located in the heat affected zone, and the fracture is characterised by brittle fracture.     

20mm厚2219铝合金可回抽搅拌摩擦焊接及接头组织和性能分析

为了解决封闭环缝的焊接匙孔问题,研究了采用可回抽搅拌摩擦焊接进行匙孔消除的焊接工艺. 在厚板可回抽焊接过程中,搅拌针末端的瞬时空腔问题受体积效应影响将更为显著且更难控制. 研究了不同回抽焊接长度下20 mm中厚板2219铝合金可回抽焊接接头的内部质量、组织形貌和力学性能. 结果表明,在焊接速度100 mm/min、搅拌头转速400 r/min的参数组合下,回抽焊接区长度为200 ~ 500 mm时,可获得无内部缺陷的可回抽搅拌摩擦焊焊缝;回抽焊接区接头横截面上存在2个焊核,靠近焊缝上表面的焊核大小随着回抽过程不断减小;一次焊接、重复焊接和可回抽焊接接头的拉伸性能依次降低,且可回抽焊接接头的力学性能随着回抽距离的增长而有所提升;在实际工程应用中回抽距离500 mm为较优的参数选择.     

常规FSW与双轴肩FSW对铝合金接头组织和性能的影响

对采用常规FSW和双轴肩FSW所得到焊接接头性能进行试验研究,测试了两种焊接得到的焊接接头的抗拉强度、屈服强度和断后伸长率,并对接头的微观组织和断口形貌进行了观察和分析.结果表明,双轴肩FSW接头横截面形成了一组由内向外扩张“洋葱环”状的椭圆环;常规FSW焊核区与热力影响区之间组织发生明显变化;硬度的最低处为双轴肩FSW前进侧热力影响区,最高处为双轴肩FSW接头上表面焊核区;常规搅拌摩擦焊接头的综合力学性能最好,双轴肩次之;断口形貌分析表明,接头断裂模式均为韧性断裂,且常规FSW断口韧窝尺寸比双轴肩FSW接头韧窝小而深,表现出更好的塑性.     

搅拌针端部形状对FSW接头根部金属流动行为的影响

采用不同端部形状的搅拌针对12 mm厚的6061-T4铝合金进行对接焊,观察了匙孔处不同横截面上焊缝形貌,分析了搅拌针端部形状变化对FSW接头根部金属流动行为的影响.结果表明,FSW焊缝区金属沿焊缝厚度方向上的迁移主要受搅拌针表面螺纹影响,而搅拌针端部锥度对接头根部金属的迁移的影响可分为两个方面,一是脱离螺纹作用的金属向下迁移,二是焊核区金属的向上迁移.搅拌针端面直径影响FSW接头未焊透厚度.随搅拌针端面直径增加,搅拌针可焊板材厚度增大.     

搅拌针锥度和螺纹头数对厚板铝合金FSW焊缝金属迁移的影响

研究了20 mm厚2024-T4铝合金板材在搅拌摩擦焊过程中,搅拌针锥度与搅拌针表面螺纹头数对焊缝塑性金属在搅拌针周围迁移程度的影响.结果表明,随搅拌针螺纹头数增加,搅拌头旋转1圈时搅拌针螺纹所转移的高温金属量增加,焊核中塑性金属在前进边和返回边的轴向上迁移程度增加,宏观表现为焊核高度、宽度和面积增大;搅拌针锥度由25°减少至15°时,焊缝塑化金属量增加,焊核塑性金属在焊缝横截面上横向和轴向的迁移程度都增大,焊核面积增大.采用多头螺纹和较小锥度的搅拌针,可以改善厚板焊接时温度梯度大、焊缝金属流动不充分的问题,保证焊缝冶金质量.     

搅拌针偏置对SR-FSW焊缝界面残留缺陷及接头力学性能的影响

系统研究了搅拌针偏置对双轴肩搅拌摩擦焊接头内部质量及接头性能的影响. 接头组织形貌结果表明,接头焊核区由存在层状结构的3个区域和不带任何趋势性分布的1个楔状区域组成. 当搅拌针偏置使接头原始装配界面置于接头后退侧塑性金属流动不充分的楔状区域时,将会产生一种特有的界面残留缺陷. 接头力学性能结果表明,随着搅拌针偏置从−6 mm变至−3 mm时,接头拉伸性能逐渐升高,均断裂于界面残留缺陷处;当搅拌针偏置处于{−2 mm,+ 5 mm}范围内时,接头性能达到最优,接头抗拉强度达到340 ~ 350 MPa,接头均断裂于后退侧热力影响区. 而当偏置进入 + 6 mm时,接头性能开始下降.     

铝合金LD10的搅拌摩擦焊组织及性能分析

搅拌摩擦焊是 2 0世纪 90年代发展起来的新型固态塑性连接方法 ,在航空航天结构中铝合金件的焊接方面有很好的应用前景。文中试验研究了航空航天结构件常用的LD10铝合金的搅拌摩擦焊技术。通过工艺试验 ,对其塑性连接时的焊缝成形、焊缝组织形态及接头的力学性能进行了分析。研究结果表明 ,用搅拌摩擦焊方法焊接板厚6mm的LD10铝合金 ,当规范参数合适时 ,可获得外观成形美观、内部无缺陷、几乎无变形的平板对接接头。从显微组织角度 ,焊接接头可分为五个区域 ,即焊核、热力影响区、热影响区、轴肩变形区和探针挤压区 ,各区域的组织有明显的特征。接头的力学性能试验表明 ,接头的抗拉强度可达母材的 87% ,高于熔焊接头的强度 ,断裂位置大多位于热影响区     

Microstructure,static and fatigue properties of refill friction stir spot welded 7075-T6 aluminium alloy using a modified tool

ABSTRACT

Defect-free joints were produced in 2.0?mm thick 7075-T6 Al alloy by refill friction stir spot welding using a modified tool. Weld performance was evaluated in terms of microstructure, interfacial bonding, hardness, static and fatigue strength based on the experimental observations. The results indicated that grain size, interfacial bonding quality and lap shear strength significantly depend on sleeve penetration depth (SPD), with sufficient interfacial bonding and stable lap shear strength achieved when SPD?≥?1.8?mm. The SPD and applied load played a dominant role in determining the static lap shear and fatigue failure mechanisms, respectively. More precisely, the lap shear failure mode was an interfacial failure when SPD?≤?1.8?mm, and nugget pullout when SPD?≥?2.0?mm. The fatigue fracture mode involved nugget pullout under high applied load, while fracture through the parent sheet occurs under medium and lower applied loads.     

搅拌针表面形状对焊缝金属轴向迁移的影响

采用不同表面形状的搅拌针对20 mm厚7075铝板进行焊接,分析其对焊缝金属沿轴向迁移的影响.结果表明,使用圆锥形搅拌针焊接时,随着旋转速度增加,焊核区面积、塑化金属沿两边向上迁移高度先增大后减小,疏松区面积则先减小后增大.同一焊缝中焊核区内塑化金属沿前进边向上迁移高度大于返回边.采用375 r/min旋转速度焊接时获得的焊核区面积、塑化金属向上迁移高度最大,疏松区面积最小.而使用三角平面搅拌针焊接时,瞬时空腔的出现增强了沿焊缝水平方向上"抽吸-挤压"效应,同时改善塑化金属沿轴向上的流动性,导致疏松缺陷消失.     

An Investigation into the Microstructure of Friction-Stir Welded and Artificially Aged AA2017

Microstructural changes in friction-stir welding (FSW) of artificially aged AA2017 were investigated. First, FSW was performed with rotational and linear speeds of 800 rpm and 40 mm/min, respectively. Then, microstructural studies by means of optical metallography and electron microscopy were conducted in different regions of the welded plates. Hardness testing was also employed to determine local strength and subsequent natural aging progress after welding. The results indicate that the considerable hardness degradation occurs in the thermo-mechanically affected zone owing to coarsening of semi-coherent precipitates. Grain refinement also takes place in the weld nugget as a result of dynamic recrystallization and it results in a fine-grained structure with the mean grain size to 5 μm. On the other hand, the initial precipitate distribution is completely vanished in the weld nugget and instead, spherical-shaped particles are formed. Moreover, natural aging after FSW occurs in the welded sample and leads to considerable increase in the hardness of the weld nugget zone.     

搅拌摩擦焊接工艺参数对AA6061-B4C焊接接头抗拉强度的影响（英文）

搅拌摩擦焊(FSW)是一种固态连接技术,可用来连接高强度铝合金及多种陶瓷颗粒增强金属基复合材料(MMCs)。搅拌摩擦焊获得的陶瓷增强金属基复合材料焊缝优良,在增强体与基体间没有发生有害反应。对搅拌摩擦焊接工艺参数对AA6061-B4C焊接接头抗拉强度的影响进行研究。采用4因素5水平的中心复合设计来控制实验的次数。构建一数学模型来分析搅拌摩擦焊工艺参数对接头抗拉强度的影响。结果表明,在旋转速度1000r/min、焊接速度1.3mm/s、轴向力10kN、增强相含量12%的条件下,搅拌摩擦焊得到的焊接接头的抗拉强度最大。根据构建的模型采用广义简约梯度算法进行优化以得到最大的抗拉强度。金相分析表明,在焊接接头中出现了多种区域,如焊合区、热力影响区和热影响区。在焊合区观察到大量的被细化的铝基体晶粒以及粒径明显减小的B4C颗粒。在热力影响区出现塑性变形、热影响和被拉长的铝晶粒。     

钛合金与铝合金复合接头的搅拌摩擦焊

为了避免搅拌头轴肩磨损及防止根部未焊透工艺缺陷,设计一种Ti/Al复合式接头,采用组合式搅拌头偏置扎入TC4钛合金与5A06铝合金对接界面进行焊接,研究其搅拌摩擦焊(FSW)工艺及组织性能. 在最佳FSW工艺条件下,完成对Ti/Al异种接头的组织结构及机械拉伸性能分析. 结果表明,接头拉伸强度达到铝合金母材强度的88.3%,断裂主要发生在铝侧焊核区内. 根据对接界面的形貌特征分析,重点讨论了Ti/Al对接界面的形成机制,认为采用较低的搅拌头转速和较小的搅拌针钛侧偏置量,可获得焊接质量较高的Ti/AlFSW接头.