AA6061-T6与AZ31合金异种搅拌摩擦焊接头的微观组织

研究了AA6061-T6和AZ31合金异种搅拌摩擦焊接头的微观组织。在异种搅拌摩擦焊接AA6061-T6与AZ31合金时,采用偏置条件,即将搅拌针插入时偏向AZ31合金,从而得到异种对接接头。通过预备实验来优化搅拌针的前进速度、旋转速度。运用电子背散射衍射技术观察搅拌区的纹理,并得到粒径分布和错位角分布,在搅拌区存在相对精细的晶粒结构。在AA6061-T6搅拌区出现随机或弱面取向,而在AZ31搅拌区出现旋转底面取向。再结晶颗粒的平均尺寸只有2．5～4．5μm。与基础合金相比,在AA6061-T6搅拌区的大角度晶界的分数增大,而在AZ31搅拌区的小角度晶界的分数降低。     

回填搅拌摩擦点焊和传统搅拌摩擦点焊AA6061-T6接头的微观结构和力学性能的比较

在搅拌摩擦点焊过程中,通过添加填充板来改善摩擦成形过程,这种新工艺被称为回填搅拌摩擦点焊。分别采用回填搅拌摩擦点焊和传统的搅拌摩擦点焊工艺焊接AA6061-T6搭接焊样品,研究搅拌头的旋转速度对接头的力学性能和金相组织的影响。在不同的旋转速度下,回填搅拌摩擦点焊接头的静态剪切强度都比传统搅拌摩擦点焊接头的好。这归因于在回填搅拌摩擦点焊时,添加了填充板从而有更多的材料来填充孔洞,消除了形成的孔洞缺陷,从而使点焊焊核区的有效截面积增加。借助扫描电镜观察讨论了材料的失效机制,分析了断裂表面形貌。2种焊接接头的硬度曲线都呈W形,最小的硬度出现在热影响区。     

6061-T6铝合金的静止轴肩搅拌摩擦焊工艺及组织性能

采用自主研制的静止轴肩搅拌摩擦焊工具系统成功获得了6061-T6铝合金的对接接头. 对该接头的焊缝成形、显微组织、硬度分布以及拉伸性能分别进行了试验研究. 结果表明,SSFSW工艺所得6061-T6铝合金接头具有非常美观的焊缝成形,与常规的FSW工艺相比,几乎没有出现焊缝减薄的现象;焊缝组织分区也有明显的不同,TMAZ非常窄,只有几百微米;接头的硬度呈"W"形分布;在转速1 000 r/min,焊速为200 mm/min时,接头的抗拉强度和断后伸长率达到最大,分别为母材的71.5%和44.6%;拉伸试样均断裂在热影响区,它是接头发生断裂的最薄弱区域.     

铝合金静止轴肩搅拌摩擦焊组织非均质性对接头力学性能的影响

对6061-T6铝合金静止轴肩搅拌摩擦焊(stationary shoulder friction stir welded, SSFSW)接头组织非均质性与力学性能的相互影响进行了定量分析. 结果表明,SSFSW焊接接头存在明显的组织非均质性,表现在晶粒尺寸及形状、沉淀相种类及分布形态不同,其中沉淀相析出不同是影响力学性能差异的主要因素. 由于组织非均质性导致紧邻焊核区的热影响区软化严重,其硬度和抗拉强度在接头区域最低,分别为母材的60%和72%,为接头最薄弱部分. 由于沉淀强化和晶粒细化效应,焊核区的强度与塑性最好,而抗拉强度和断后伸长率分别达到母材的88%和215%. 随着与焊核区距离的增加,热影响区抗拉强度和屈服强度逐渐增加,断后伸长率不断降低.     

转速对6082-T6铝合金搅拌摩擦焊焊接接头织构的影响

采用电子背散射衍射技术,借助取向成像分析软件,研究了搅拌头在不同转速下,6082-T6铝合金搅拌摩擦焊焊核区上表面晶粒形貌、晶界特征、织构组分的演化. 结果表明,在搅拌针所引入的剪切应力作用下,焊核区形成(110)[001]高斯织构和(114)[$ 22 {\\bar 1} $]织构,轴肩的顶锻压力使其沿着TD方向旋转一定角度,形成(112)[$ 11 {\\bar 1} $]铜织构,随着搅拌头转速的提高,晶粒沿着TD方向旋转角度增加,进一步形成(100)[011]剪切织构和($ 11 {\\bar 1} $)[112]织构;焊核区晶粒受到搅拌针的挤压而形成[110]丝织构,搅拌头转速从1 200 r/min提高到2 000 r/min时,挤压程度增加,导致[110]丝织构组分显著增多.     

6061-T6铝合金双轴肩搅拌摩擦焊接头组织与力学性能

针对6 mm厚6061-T6铝合金板材,在主轴转速800 r/min,焊接速度150 mm/min参数下实现双轴肩搅拌摩擦焊接,并对一部分试件进行焊后热处理。对焊态试件和焊后热处理试件同时进行金相试验、拉伸试验和显微硬度试验对比分析。在焊态下,接头平均抗拉强度为203 MPa,达到母材的64%,接头在焊缝区32 mm的宽度区域内显微硬度出现不同程度的下降,显微硬度分布呈"W"型;接头经焊后热处理后,焊态下溶解消失的强化相重新析出,使接头组织重新得到强化,热处理态接头平均抗拉强度为292 MPa,达到母材的92%,整个焊缝区显微硬度均得到提高,焊态下"W"型显微硬度分布规律消除。     

Microstructure and mechanical properties of friction stir welded thin sheets of 2024-T4 aluminum alloy

Friction stir welding （FSW） is a new and promising welding processing that can produce low-cost and high-quality joints of aluminum alloys. 1 mm thick sheets of 2024-T4 aluminum alloys which are always used as building and decorating materials were welded by FSW. The microstructure and mechanical properties of fiiction stir welded 1 mm thick sheets of 2024-T4 aluminum alloy were studied. It was found that the thinner the 2024 aluminum alloy, the larger the FSW technological parameters field. The grains size of weld nugget zone （WNZ） is approximately 10 times smaller than that of the parent material, but the second phase in the material is not refined apparently in the welding. The FS welded joints have about 40% higher yield strength than the parent material, but the elongation of FS welded joints is under about 50% of the parent material. The electron backscattered diffraction （EBSD） results show that there are much more low angle boundaries （LAB） in WNZ than that in parent material, which indicates that FSW causes a number of sub-grain structures in WNZ, and this is also the reason of the increase of yield strength and Vickers hardness of the welded joint.     

6082-T6铝合金搅拌摩擦焊组织演变与力学性能

通过透射电子显微镜、扫描电子显微镜、拉伸试验机和显微硬度计对6082-T6铝合金搅拌摩擦焊接头焊缝区组织演变和力学性能进行分层研究. 结果表明,在焊核区上层,材料发生塑性变形,晶格畸变能增加,为降低能量,大量的位错集聚成亚结构边界发生动态回复. 同时在焊接热循环的作用下发生动态再结晶,导致焊缝区上层晶粒细小. 在焊核区下层,主要受到搅拌针搅拌作用,轴肩产热通过扩散过程传递到下层的热量减少,发生动态回复和动态再结晶程度低于焊缝上层,晶粒粗大. 前进侧和后退侧热影响区均出现棒状β′沉淀相. 对应焊缝上、下两层硬度都呈“W”形分布,焊缝上层硬度高于焊缝下层硬度,最小值出现在前进侧. 沿着焊缝长度方向上层和下层的抗拉强度分别为205,186 MPa,呈降低趋势,为韧性断裂.     

Rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys

The tensile rupture locations of friction stir welded joints of AA2017-T351 and AA6061-T6 aluminum alloys were examined. The experiments show that the rupture locations of the joints are different for the two aluminum alloys, which are influenced by the welding parameters. When the joints are free of welding defects, the AA2017-T351 joints are ruptured in the weld nugget adjacent to the thermo-mechanically affected zone on the advancing side and the rupture surfaces appear as oval contours of the weld nugget, while the AA6061-T6 joints are ruptured in the heat affected zone on the retreating side and the rupture surfaces are inclined at a certain degree to the bottom surfaces of the joints. When welding defects are present in the joints, the AA2017-T351 joints are ruptured in the weld center, while the AA6061-T6 joints are ruptured on the retreating side near the weld center. The rupture locations of the joints are dependent on the internal structures of the joints and can be explained through them.     

6016-T4和5182-O铝合金回填式搅拌摩擦点焊力学性能研究

利用回填式搅拌摩擦点焊(FSSW)技术焊接6016-T4和5182-O异种金属接头,研究其显微组织及力学性能。以剪切拉伸性能为评价指标,得出最优工艺参数是:下压深度1.5 mm,旋转速度2200 r/min,焊接时间2.5 s,平均剪切力2 950 N。疲劳极限载荷F=296 N,疲劳断裂时裂纹起源于上下板搭接处,同时向板厚和板宽方向扩展。接头显微组织中没有铸态的柱状晶,均为等轴晶和较母材晶粒略有长大的组织,接头性能良好。     

Static shear strength and fatigue life of refill friction stir spot welded AA 6061-T6 sheets

This study was aimed at evaluating the static shear strength and fatigue properties of the newly developed refilled friction stir spot welded AA 6061-T6 joints. The keyhole, the process disadvantage of conventional friction stir spot welding, was refilled successfully, using an additional filler plate, with specially designed tools. Two different tool profiles, namely, convex and concave, were used for the refilling process. Sound and defect free joints were obtained by the refilling process. Joints refilled with convex tools showed better static shear strength than those with the concave ones. The variation of microhardness in different regions of the weld was analysed. Fatigue tests were conducted on the lap shear specimens at a stress ratio of R?=?0·1. The optical micrographs of the welds after fatigue failure in both the conventional and refilled processes were examined to study the fatigue crack propagation and failure modes.     

7050-T7451铝合金搅拌摩擦焊接头组织和性能与疲劳断裂

文中主要对7050-T7451铝合金搅拌摩擦焊焊接接头组织性能和疲劳断裂进行研究,对焊件进行金相组织、硬度、疲劳试验,并根据试验结果进行分析。试验结果表明,焊核区和热力影响区组织有明显的分界,整个接头表面和截面的不同区域的组织有明显的不同,焊核区经历高温热循环,并且受到强烈的搅拌作用,发生了显著的动态再结晶,组织均匀细小,没有明显的方向性。热力影响区组织在搅拌摩擦焊接过程中主要受到热循环作用的影响,同时一定程度上受到了机械外力的作用,产生了较小的塑性变形,但储能不够,最终未出现动态再结晶。热影响受到热循环的作用,组织比母材要粗大,但没有发生明显塑性变形,仍具有母材纤维组织的特点。硬度试验的结果表明,母材区和焊核区的硬度比较大,而热影响区的硬度偏低,热力影响区的硬度在它们之间。通过对疲劳试验分析,应力水平为200 MPa时,试样在前进侧热影响区发生断裂,断口的表面较为粗糙。应力水平为250 MPa时,试样在焊核区发生断裂,断口表面较为平整。应力水平为300 MPa时,试样在母材处发生断裂,断口表面十分平整。创新点： 通过搅拌摩擦焊工艺形成的7050-T7451铝合金焊接接头,成形良好,技术优势突出,适用于航天航空等多个重要领域。     

6013—T4铝合金薄板搅拌摩擦焊热输入对焊缝成形及组织性能的影响

针对2 mm厚6013—T4铝合金薄板进行了搅拌摩擦焊接工艺试验,用搅拌头旋转速度和焊接速度的比值ω/v表征搅拌摩擦焊的热输入,试验研究了焊接热输入对接头的焊缝成形和力学性能的影响,并分析了接头的显微组织.结果表明,搅拌摩擦焊接头的综合性能较好,抗拉强度和屈服强度分别达到母材的83.3%和75.8%;在不同的搅拌头旋转速度下,随着焊接热输入的增加,接头的屈服强度和抗拉强度降低;ω/v在3 r/mm左右,焊缝成形美观,飞边毛刺少.母材为板条状组织;热影响区晶粒与母材相似,但稍微有粗化;热力影响区的晶粒极不均匀,既有等轴晶,也有拉长的带状组织;焊核区为细小的等轴晶组织.     

厚板铝合金搅拌摩擦焊接头组织及性能沿厚度方向的变化规律

通过分层法对30 mm厚7A05-T6铝合金搅拌摩擦焊接头焊核区不同位置的微观组织、力学性能进行了研究.结果表明,上表层附近的再结晶晶粒尺寸最大;当旋转频率为360 r/min,焊接速度为100 mm/min时,TI到T5层的抗拉强度分别为326,354,342,334和307 MPa,呈先高后低的趋势,且屈服强度和断后伸长率也呈一样的趋势;微观断口中存在大量的网状韧窝,其中分层切片T2上韧窝最深.显微硬度分布为焊缝上部高于下部,沿焊缝中心不对称分布.随厚度增加,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.     

6mm厚6061-T6铝合金双轴肩搅拌摩擦焊工艺方法研究

针对6 mm厚6061-T6铝合金板材,设计制造了不同结构形式和尺寸规格的双轴肩搅拌摩擦焊工具,并对搅拌摩擦焊工具的结构形式和尺寸规格对焊接过程及焊接接头质量的影响进行了系统的分析研究：设计制造了两体式和三体式双轴肩搅拌摩擦焊工具,并对两种结构形式进行分析;设计制造了环状轴肩和凹面轴肩,通过焊接工艺试验得知凹面轴肩焊缝成形性优于环状轴肩;设计制造了正-反螺纹搅拌针、正螺纹搅拌针、整圆柱搅拌针和圆柱铣扁搅拌针;圆柱铣扁搅拌针焊缝焊接质量优于其他三种结构形式的搅拌针。采用凹面轴肩和圆柱铣扁搅拌针组装成的搅拌头,对6 mm厚6061-T6铝合金板材进行焊接,在主轴转速为800 r/min、焊接速度为150 mm/min工艺参数下,焊接接头得到最大抗拉强度值为220MPa,达到母材抗拉强度（315 MPa）的70%。     

镁合金AZ31搅拌摩擦焊接头的微观组织

采用搅拌摩擦焊接法焊接了镁合金AZ31, 研究了焊接参数对焊接接头微观组织和显微硬度的影响. 结果表明 焊接接头成形良好, 焊缝没有气孔、裂纹和夹渣, 焊缝区的显微硬度比母材稍有降低, 但降低幅度不大.     

2219-T87厚板搅拌摩擦焊沿厚度方向的性能差异

采用搅拌摩擦焊方法对35 mm厚的2219-T87高强铝合金进行了单道对接焊.结果表明,焊缝的抗拉强度可达274 MPa,且断裂于焊核区.用螺旋形搅棒焊接厚板时,焊接速度较慢,焊核区上部组织因温度较高,同时在螺旋产生的向下泵吸作用下,会产生比较粗大的疏松组织;而焊核区中下部组织则因温度较低,并在螺旋推力作用下形成比较细小的致密组织.焊核区上部的显微硬度存在一个下陷区,而中下部的显微硬度变化较为平缓.焊接厚度过大时,螺旋搅棒的泵吸作用引起焊核区上部组织疏松,并使其显微硬度下陷,是造成厚板搅拌摩擦焊缝强度不高且断裂于焊核区的原因.     

2219-T6激光同轴辅助搅拌摩擦焊性能与组织分析

对2219-T6铝合金激光同轴辅助搅拌摩擦焊接头的宏观形貌、力学性能及显微组织进行了研究.结果表明,激光辅助热源的加入有助于消除金属塑性流动不充分引起的隧道缺陷,提升接头性能,但激光功率过大会加剧焊缝软化而使性能下降.激光辅助热源使焊核区扩大,且焊核区中θ相（Al₂Cu）增大,但对热力影响区的显微组织无明显影响.通过固溶+人工时效方法的焊后热处理以显著提升接头强度（从母材强度的76%提升100%）.加入激光的焊核区及热力影响区在热处理后晶粒尺寸相比不加入激光有所减小,且激光功率越大,对应的晶粒尺寸越小.     

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.     

Effects of processing parameters on corrosion properties of dissimilar friction stir welds of aluminium and copper

The influence of friction stir welding processing parameters on dissimilar joints conducted between aluminium alloy (AA5754) and commercially pure copper (C11000) was studied. The welds were produced by varying the rotational speed from 600 to 1200 r/min and the feed rate from 50 to 300 mm/min. The resulting microstructure and the corrosion properties of the welds produced were studied. It was found that the joint interfacial regions of the welds were characterized by interlayers of aluminium and copper. The corrosion tests revealed that the corrosion resistance of the welds was improved as the rotational speed was increased. The corrosion rates of the welds compared to the base metals were improved compared with Cu and decreased slightly compared with the aluminium alloy. The lowest corrosion rate was obtained at welds produced at rotational speed of 950 r/min and feed rate of 300 mm/min which corresponds to a weld produced at a low heat input.