AZ31镁合金搅拌摩擦焊接头断裂机制

对AZ31镁合金搅拌摩擦焊接头进行力学性能实验.拉伸、疲劳实验结果显示,AZ31镁合金搅拌摩擦焊接头抗拉强度可以达到母材强度的92.9%,断裂位置在前进面的机械热影响区,认为是前进面机械热影响区不均匀的层状组织和应力集中作用的结果.扫描电镜显示:断口有明显的撕裂纹和纤维状组织.     

Joint properties of dissimilar Al6061-T6 aluminum alloy/Ti–6%Al–4%V titanium alloy by gas tungsten arc welding assisted hybrid friction stir welding

Hybrid friction stir butt welding of Al6061-T6 aluminum alloy plate to Ti–6%Al–4%V titanium alloy plate with satisfactory acceptable joint strength was successfully achieved using preceding gas tungsten arc welding (GTAW) preheating heat source of the Ti alloy plate surface. Hybrid friction stir welding (HFSW) joints were welded completely without any unwelded zone resulting from smooth material flow by equally distributed temperature both in Al alloy side and Ti alloy side using GTAW assistance for preheating the Ti alloy plate unlike friction stir welding (FSW) joints. The ultimate tensile strength was approximately 91% in HFSW welds by that of the Al alloy base metal, which was 24% higher than that of FSW welds without GTAW under same welding condition. Notably, it was found that elongation in HFSW welds increased significantly compared with that of FSW welds, which resulted in improved joint strength. The ductile fracture was the main fracture mode in tensile test of HFSW welds.     

镁合金高转速搅拌摩擦焊工艺研究

目的 研究镁合金高转速搅拌摩擦焊工艺及其对组织与性能的影响规律。方法 采用光学显微镜观察以及拉伸性能测试等方法,探索了1.5 mm厚AZ31B镁合金高转速搅拌摩擦焊接工艺,对其接头组织与力学性能进行了测试分析。结果 采用6000 r/min转速时,随着焊速从600 mm/min降低至100 mm/min,焊接接头隧道型孔洞缺陷消失;采用600 mm/min焊速时,2000~4000 r/min转速范围内可获得无缺陷的接头。拉伸测试结果表明,6000 r/min-100 mm/min焊接工艺下接头的拉伸性能最优,抗拉强度为235.33 MPa,为母材强度的87.92%。结论 镁合金采用高转速搅拌摩擦工艺可获得无缺陷的焊接接头,且采用高转速匹配低焊速的工艺可使接头的拉伸性能得到提升。     

铝/镁搅拌摩擦焊-钎焊焊接接头微观组织结构

目的研究不同工艺参数下钎料Zn的添加对Al/Mg异种金属搅拌摩擦焊-钎焊焊接接头组织和性能的影响。方法以厚度为0.05 mm的纯Zn作为钎料,对3 mm厚的2A12-T4态铝合金和4 mm厚的AZ31变形镁合金,进行搅拌摩擦焊-钎焊的复合焊接,分析锌夹层的添加对接头微观组织与力学性能的影响。结果当添加Zn中间层时,接头钎焊区缓解了拉伸断裂趋势,在焊接速度为23.5 mm/min,旋转速度为375 r/min时,接头抗拉剪力达到5.5 k N,复合焊接接头的钎焊焊缝由搭接区、固相扩散区、钎焊区组成。结论钎料的添加有效阻止了Al-Mg系金属间化合物的形成。     

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%。     

Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy

Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.     

A general strategy for the reliable joining of Al/Ti dissimilar alloys via ultrasonic assisted friction stir welding

Ultrasonic assisted friction stir welding (UaFSW) was used to join 6061-T6 aluminum and Ti6Al4V alloys. A small plunge depth endowed with the low heat input was used and the sound joints without obvious thickness reduction were achieved. A diffusion-type bonding without the intermetallic compounds layer was observed at the joint interface. The ultrasonic improved the diffusion thickness and decreased the average size of grains and titanium alloy fragments. A hook-like structure was formed at the bottom interface of the UaFSW joint, which improved the bonding length and the mechanical interlocking. The microhardness of the stir zone was increased because of the further grain refinement induced by ultrasonic. The maximum tensile strength of the UaFSW joint was 236 MPa, which reached 85% of the base 6061-T6 alloy.     

工艺参数对Al-Mg异种金属搅拌摩擦焊-钎焊复合焊接接头力学性能的影响

目的研究工艺参数对Al-Mg异种金属搅拌摩擦焊-钎焊复合焊接接头力学性能的影响。方法采用搅拌摩擦焊-钎焊方法,在不同焊接工艺参数下焊接2A12-T4铝合金和AZ31镁合金。结果当焊接速度为23.5mm/min、旋转速度为375 r/min时,焊接接头的抗拉剪力达到最大,为5.5 kN,比搅拌摩擦焊接头的最大抗拉剪力的5.0 kN提高了10%。结论搅拌摩擦焊-钎焊复合焊接的工艺参数会显著影响铝/镁异种金属接头力学性能,通过优化工艺参数能够获得力学性能优异的铝/镁异种金属焊接接头。复合焊接接头的抗拉剪力随着焊接速度的增大呈现先增大后减小的趋势。     

铝合金超声辅助搅拌摩擦焊接接头组织性能研究

目的探究超声振动对铝合金搅拌摩擦焊的作用效果。方法分别采用普通搅拌摩擦焊和超声辅助搅拌摩擦焊方法,对7075铝合金进行焊接试验,并对焊接接头的微观组织、力学性能、断口形貌进行分析。结果普通搅拌摩擦焊焊缝中生成了隧道型缺陷,施加超声振动后,缺陷消失,形成了无缺陷的良好接头,且与普通搅拌摩擦焊相比,超声辅助搅拌摩擦焊焊缝热影响区晶粒长大程度较小,焊核晶粒细化。接头强度明显提高,达到铝合金母材强度的71.5%,接头断裂模式为韧窝和准解理的混合断裂形式。结论超声振动促进了塑性金属的流动,能有效抑制孔洞、隧道型缺陷等的形成,同时超声振动能在提升金属塑性的同时,降低焊缝的热输入。     

60mm厚度6061-T6铝合金板搅拌摩擦焊接接头微观组织与力学性能

采用搅拌摩擦焊接方法对6061-T6铝合金板进行了60mm双面对接焊实验,研究了搅拌摩擦焊接接头的微观组织与力学性能,结果表明:焊缝区微观组织沿厚度方向发生了不同程度的改变,焊接接头强度达到218MPa,为母材强度的70％;焊接热循环引发的金属强化相“重固溶”和“过时效”是接头力学性能下降的重要原因,其中前进侧热机影响...     

Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响

研究了Ce对Mg-Al-Zn系合金焊接接头显微组织及力学性能的影响,结果表明,稀土Ce对改善AZ31、AZ61合金接头强度及提高接头有效系数有明显作用,添加1.0%Ce将使AZ31合金的焊接接头有效系数由0.66提高到0.81。Ce能改善Mg-Al-Zn合金焊接性的原因是Ce与Al形成高熔点的Al4Ce相,减少了粗大的Mg17Al12相的数量并细化了焊缝区的晶粒。通过分析AZ31、AZ61Ce镁合金焊接熔池的特点和结晶过程,获得了焊缝边缘区域依托母材未熔晶粒形核与长大的联生生长机制。     

镁合金搅拌摩擦焊接工艺参数优化

为了优化镁合金搅拌摩擦焊接工艺参数,对5 mm厚镁合金AZ31B板材的搅拌摩擦焊接技术进行了试验研究,利用SN比实验设计,对镁合金AZ31B搅拌摩擦焊接工艺参数进行了方差分析,优化了搅拌头的材料、结构,最终确定搅拌头的材料为W6Mo5Cr4V2,结构为凹面圆台形.轴肩尺寸为12 mm.探针的根部直径为5.5 mm,端部直径为2.5 mm,长度为4.7 mm.获得镁合金AZ31B搅拌摩擦焊的工艺参数显著性顺序为旋转速度、横向速度和压力;确定了镁合金AZ31B搅拌摩擦焊的最优工艺参数为1500 r/min、47.5 mm/min、3kN.     

Superplastic Forming of Friction Stir Welded AA6061-T6 Alloy Sheet with Various Tool Rotation Speed

This study attempts to investigate the superplastic forming (SPF) of friction stir welded (FSW) AA6061-T6 alloy sheet at various tool rotation speeds in the range of 500 to 2000 rpm. The effect of FSW on SPF free blow forming of AA6061-T6, pole height, pole thickness, equivalent strain rate, and equivalent flow stress were investigated at constant pressure and constant temperature. Using the Cheng model the pole thickness, the equivalent strain rate, and equivalent flow stress were determined from superplastic free blow forming experiment. The finite element modeling and simulation is performed over the SPF of FSW specimens using selective superplasticity method. Experimental results indicate that tool rotation speed is the critical parameter during friction stir welding that has a greater influence on SPF. The theoretical modeling results exhibit that the SPF of friction stir welding can be practically applied to determine pole thickness, strain rate, flow stress, and strain rate sensitivity index. The finite element modeling results were found to be fairly agreeing with the experimental results. Hence, superplasticity can be significantly enhanced by friction stir welding by varying the FSW tool rotation speed.     

Process optimization in the self-reacting friction stir welding of aluminum 6061-T6

Self-reacting friction stir welding (SR-FSW), also called bobbin-tool friction stir welding (BT-FSW), is a solid state welding process similar to friction stir welding (FSW) except that the tool has two opposing shoulders instead of the shoulder and a backing plate found in FSW. The tool configuration results in greater heat input and a symmetrical weld macrostructure. A significant amount of information has been published in the literature concerning traditional FSW while little has been published about SR-FSW. An optimization experiment was performed using a factorial design to evaluate the effect of process parameters on the weld temperature, surface and internal quality, and mechanical properties of self-reacting friction stir welded aluminum alloy 6061-T6 butt joints. The parameters evaluated were tool rotational speed, traverse speed, and tool plunge force. A correlation between weld temperature, defect formation (specifically galling and void formation), and mechanical properties was found. Optimum parameters were determined for the welding of 8-mm-thick 6061-T6 plate.     

6082-T6铝合金搅拌摩擦焊接头的显微组织与力学性能

对8mm厚的6082-T6铝合金进行了搅拌摩擦焊接试验,焊后对工艺参数与接头显微组织及力学性能的关系进行了分析。结果表明：焊核区显微组织为细小等轴晶组织。分析焊接速度对接头抗拉强度的影响得出规律：随着焊接速度的增大,接头强度增大,但焊接速度达到一定值时,接头性能达到最高值,之后随着焊接速度变大,接头就会出现缺陷,影响接头的性能。     

Effects of tool rotational and welding speed on microstructure and mechanical properties of bobbin-tool friction-stir welded Mg AZ31

The effects of rotational and welding speeds on the microstructure and mechanical properties of bobbin-tool friction stir welded (BT-FSW) Mg AZ31 were investigated. The results indicated that the thermo-mechanically affected zone (TMAZ) consisted of equiaxed grains, which were inconsistent with the deformed, rotated and elongated grains found in the TMAZs of bobbin-tool friction stir welded Al alloys and friction stir welded Al and Mg alloys. The average grain size increased as the ratio of the rotational speed to welding speed increased. Excellent welds with no degradation in hardness were produced using a low heat input. Mechanical tests revealed that the ultimate tensile strengths gradually increased with increasing welding speed while keeping the rotational speed constant. The rotational and welding speeds had only slight influences on the yield stress and fracture elongation.     

Microstructure and Mechanical Properties of Friction Stir Lap Welded Aluminum Alloy AA2014

Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools (with triangular and threaded taper cylindrical pins). The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets (i.e., no Alclad) were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made (with threaded taper cylindrical tool) in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition (43%) was considerably lower (because of the higher base material strength) than those made in T4 condition (51%). The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.     

焊速对水下搅拌摩擦焊接7A04铝合金组织性能的影响

对7A04-T6铝合金板进行了水下搅拌摩擦焊接(Submerged friction stir welding,SFSW),研究了焊速对焊接接头组织和力学性能的影响。结果表明:采用SFSW成功实现了7A04铝合金的连接,晶粒细化和细小、弥散分布的析出相有效减弱了焊接热软化效应。当旋转速度恒定为950r/min,焊速从95mm/min增大到235mm/min时,接头焊核区的晶粒和析出相随着焊速的增大逐渐细化,抗拉强度系数从84.5%升高到89.0%。不同焊速条件下,拉伸断口均呈现微孔聚合和解理混合断裂特征。     

转速对6061铝合金搅拌摩擦搭接焊接头组织和力学性能的影响

目的 研究不同转速条件下6061铝合金搅拌摩擦搭接焊接头组织和力学性能的变化规律,为工程实践应用提供参考。方法 在不同旋转速度（800、1 200、1 500 r/min）下对4 mm厚的6061铝合金进行搅拌摩擦搭接焊实验,固定进给速度和轴肩下压量,研究搅拌头转速对接头宏观组织、微观组织和力学性能的影响。结果 所有接头均没有出现明显缺陷,当转速为1 500 r/min时,搅拌区晶粒尺寸细化明显,最大失效载荷达到母材的75%,上板和下板的硬度曲线都呈“W”形;当转速为800 r/min和1 200 r/min时,下板硬度曲线呈“V”形。随着转速的增大,有效搭接宽度逐渐增大,接头的平均拉剪强度也在增大,所有接头都在前进侧断裂,断裂形式均为拉伸断裂。结论 转速的提升增加了焊接热输入量和机械搅拌作用,促进了有效搭接宽度的增大和晶粒尺寸的细化,但未能改变钩状缺陷的形成及延伸方向。当转速为1500r/min时,热输入量较大,搅拌区范围相对较大,下板存在更大面积的搅拌区,其硬度规律与上板的相似。所有接头均为拉伸断裂,断裂位置在热影响区附近,说明搭接接头连接良好。     

Tensile Fracture Location Characterizations of Friction Stir Welded Joints of Different Aluminum Alloys

The tensile fracture location characterizations of the friction stir welded joints of the AA1050-H24 and AA6061-T6 Al alloys were evaluated in this study. The experimental results show that the fracture locations of the joints are different for the different Al alloys, and they are affected by the FSW parameters. When the joints are free of welding defects, the AA1050-H24 joints are fractured in the HAZ and TMAZ on the AS and the fracture parts undergo a large amount of plastic deformation, while the AA6061-T6 joints are fractured in the HAZ on the RS and the fracture surfaces are inclined a certain degree to the bottom surfaces of the joints. When some welding defects exist in the joints, the AA1050-H24 joints are fractured on the RS or AS, the AA6061-T6 joints are fractured on the RS, and all the fracture locations are near to the weld center. The fracture locations of the joints are dependent on the internal structures of the joints and can be explained by the microhardness profiles and defect morpho