共查询到19条相似文献,搜索用时 187 毫秒
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针对3 mm厚的2024-T4铝合金,采用ABAQUS软件建立静止轴肩搅拌摩擦焊热源三维模型,分析2024-T4铝合金静止轴肩搅拌摩擦焊温度场和应力场的有限元模拟,研究了恒定150 mm/min焊接速度下,旋转速度从800 mm/min到1 200 mm/min对焊接接头残余应力的影响。结果表明:常规搅拌摩擦焊焊缝横截面高温区域呈现碗状分布,而静止轴肩搅拌摩擦焊呈类似于搅拌针形貌分布。相比于常规搅拌摩擦焊,静止轴肩可以获得更窄的搅拌区宽度,并且有效降低焊缝中心的峰值温度。焊后垂直于焊缝区域的纵向残余应力呈现“M”形分布,随着搅拌头旋转速度的增大,两种工艺下的焊后残余应力均增大。此外,静止轴肩在焊接过程中对焊缝区域持续碾压,使得焊后试样的纵向残余应力峰值相比较于传统搅拌摩擦焊能降低45.6%。 相似文献
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以0.5 mm厚LF3薄壁铝合金微搅拌摩擦焊搭接过程为研究对象,采用超小轴肩搅拌工具,研究了其无倾角微搅拌摩擦焊接过程,重点分析了微观组织分布特点和接头力学性能.采用内聚花纹锥形超小轴肩搅拌工具,依靠轴肩及搅拌针花纹的材料内聚效果,降低了焊缝宽度,焊缝宽度仅为3 mm,为微小薄壁壳体的焊接封装问题提供了可行的解决方案.搅拌工具的超高旋转频率运动,将搭接界面进行了充分的搅拌、混合和破碎,优于传统搅拌摩擦焊的Hook搭接界面.微搅拌摩擦焊搭接接头承载能力平均达到母材承载能力的89.6%. 相似文献
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利用自行设计的静止轴肩装置对6005A-T6铝合金进行了静止轴肩搅拌摩擦焊的试验研究.结果表明,当焊接速度为200 mm/min时,表面光滑且无缺陷的焊接接头抗拉强度与断后伸长率随着搅拌头旋转频率的增加呈现先增加后减小的趋势;焊接接头的正背弯180°无裂纹;当旋转频率为1800 r/min时,抗拉强度达到最大值234 MPa,接头强度系数达到79%.静止轴肩搅拌摩擦焊接头的显微维氏硬度呈W形分布,最小值出现在前进侧的热影响区;接头的软化程度随搅拌头旋转频率的增加而增加.焊接接头的断裂位置位于热力影响区,断口呈韧性断裂. 相似文献
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以在航空领域有广泛应用前景的2 mm厚2060-T8 Al-Li合金为研究对象,进行了搅拌摩擦焊对接接头的试验分析,重点研究焊接工艺参数影响焊接接头成形的规律.研究结果表明,呈碗形的焊缝由轴肩作用区与焊核区组成;轴肩作用区的等轴晶的晶粒大于焊核区.当搅拌头的转速为800 r/min且焊接速度为80 mm/min时,焊接接头的表面成形良好且内部无缺陷.与800 r/min,80 mm/min相比,提高旋转频率或降低焊接速度,焊缝表面变得较粗糙;降低旋转频率或提高焊接速度,焊缝内部会出现隧道型缺陷. 相似文献
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以AA6056铝合金单静止上轴肩双轴肩搅拌摩擦焊(stationary upper shoulder bobbin tool friction stir welding,SSUBT-FSW)接头为研究对象,通过数值模拟与试验相结合的方法,阐明了SSUBT-FSW温度场与应变场分布规律及接头成形机理. 结果表明,SSUBT-FSW的上轴肩处于静止状态,有效增加了焊接稳定性,并将最大扭矩减小至55 N·m(常规双轴肩搅拌摩擦焊最大扭矩65 N·m). 静止上轴肩对焊缝表面施加顶锻压力,促使弧纹的波峰与波谷的高度差从60 μm减小至10 μm,显著提高了接头表面光洁度. 下轴肩旋转所产生的塑性应变区直径大于搅拌针,促使接头横截面等效塑性应变场呈梯形分布,与横截面温度场具有高度吻合性. SSUBT-FSW过程中产生材料非对称性流动行为,靠近下轴肩的材料流动性显著优于静止上轴肩. 相似文献
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I. Galvão R.M. Leal D.M. Rodrigues A. Loureiro 《Journal of Materials Processing Technology》2013,213(2):129-135
The aim of this work is to study the influence of the shoulder geometry on friction stir welding of 1 mm-thick copper-DHP plates. The welds were produced using three different shoulder geometries, flat, conical and scrolled, and varying the rotation and traverse speeds of the tool. The flat shoulder tool proved to be inadequate for performing welds, because many defects were produced for all welding conditions. In turn, the scrolled shoulder tool is more effective than the conical one in the production of defect free welds. However, both geometries required a minimum rotational speed to avoid internal defects. For the same welding parameters, greater grain refinement, higher hardness and improved strength are also achieved in the nugget of the welds, using the scrolled tool. 相似文献
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采用钨铼合金搅拌工具对T4003铁素体不锈钢进行搅拌摩擦焊接工艺试验,研究搅拌摩擦焊缝成形、接头组织特征及缺陷形成机理.结果表明,不同旋转速度下随焊接速度增加,轴向压力呈单调增加趋势;当转速为150,250 r/min时,可获得无缺陷致密焊缝;当转速为350 r/min时,靠近前进侧的焊缝区出现孔洞缺陷,随着焊接速度和轴向压力不断增加,焊接缺陷有减少趋势.焊接接头焊核区发生了相变和明显淬硬现象,组织为细小等轴铁素体和低碳马氏体,焊缝具有明显不均匀硬度分布.提出了一种焊缝热塑性金属平衡流动模型分析其缺陷形成机理. 相似文献
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采用静轴肩搅拌摩擦焊接法(SSFSW)在不同的焊接速度下制备了2A14-T4铝合金T形接头。在优化的焊接工艺参数下,可以得到光滑的T形接头焊缝表面。结果表明:焊接熔核区(WNZ)的显微组织为完全动态再结晶产生的细小等轴晶,第2次焊核区(WNZ2)的平均晶粒尺寸最大,焊接重合区(WNOZ)次之,第1次焊核区(WNZ1)的平均晶粒尺寸最小。WNZ的再结晶机制主要是几何动态再结晶,并伴有部分连续动态再结晶。WNZ1和WNZ2织构类型为弱{111}<110>,而WNOZ经过2次搅拌后织构类型为弱{100}<001>。热机械影响区(TMAZ)发生塑性变形,而热影响区(HAZ)只受到焊接热循环作用,不发生塑性变形和晶粒的动态再结晶。WNZ的硬度较高,硬度最低的区域位于靠近TMAZ的HAZ。随着焊接速度的增加,接头抗拉伸强度先增大后减小。底板和加强板的主要断裂形式是脆性/韧性混合断裂。 相似文献
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In the present investigation, friction stir spot welding on annealed aluminum alloy AA5754 sheets was performed. The influences of the tool rotational speed and tool stirring (dwell) time on the weld structure and static strength of welds were evaluated. The results revealed that the width of the completely metallurgical-bonded region increases with the increasing tool rotational speed and/or the dwell time up to certain levels. Increasing such parameters beyond these levels slightly reduces the width of the bonding region. The stirred zone exhibited higher microhardness than that of the base material. The tensile-shear force was found to increase with the increasing tool rotational speed and/or dwell time up to a certain level (9s). Higher tool rotational speeds and/or prolonged dwell times slightly reduce(s) the tensile-shear force. 相似文献
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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. 相似文献
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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。 相似文献
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Effect of tool geometry on microstructure and static strength in friction stir spot welded aluminium alloys 总被引:2,自引:0,他引:2
Yasunari Tozaki Yoshihiko Uematsu Keiro Tokaji 《International Journal of Machine Tools and Manufacture》2007,47(15):2230-2236
The effect of tool geometry on microstructure and static strength in friction stir spot welds of 6061 aluminium alloy sheets was studied. Tools with three different probe lengths were used to join the aluminium sheet with different tool rotational speeds and tool holding times. The weld microstructures varied significantly depending on probe length, tool rotational speed and tool holding time. Two particular aspects were identified: the thickness of the upper sheet under the shoulder indentation and the nugget size. The former decreased with increasing probe length at the shortest tool holding time and the slowest tool rotational speed, but there were no discernible differences in other welding conditions, while the latter increased with increasing probe length, tool rotational speed and tool holding time. The tensile shear strength increased with increasing probe length, while the cross-tension strength was not affected significantly by probe length. Two fracture modes were observed: shear fracture of the nugget and mixed mode fracture under tensile shear loading, and nugget debonding and pull-out under cross-tension loading. Based on experimental observation of the microstructures, the effect of probe length on static strength and the fracture mechanisms were discussed. 相似文献
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It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for medium-thick plates due to the inherent high heat generation rate at the shoulder-workpiece contact interface in conventional friction stir welding. Thus, double-side friction stir welding is innovatively applied to join 12-mm medium-thick 6061-T6 aluminum alloy and pure copper dissimilar plates, and the effect of welding speeds on the joint microstructure and mechanical properties of Al/Cu welds is systematically analyzed. It reveals that a sound Al/Cu joint without macroscopic defects can be achieved when the welding speed is lower than 180 mm/min, while a nonuniform relatively thick intermetallic compound (IMC) layer is formed at the Al/Cu interface, resulting in lots of local microcracks within the first-pass weld under the plunging force of the tool during friction stir welding of the second-pass, and seriously deteriorates the mechanical properties of the joint. With the increase of welding speed to more than 300 mm/min void defects appear in the joint, but the joint properties are still better than the welds performed at low welding speed conditions since a continuous uniform thin IMCs layer is formed at the Al/Cu interface. The maximum tensile strength and elongation of Al/Cu weld are, respectively, 135.11 MPa and 6.06%, which is achieved at the welding speed of 400 mm/min. In addition, due to the influence of welding distortion of the first-pass weld, the second-pass weld is more prone to form void defects than the first-pass weld when the same plunge depth is applied on both sides. The double-side friction stir welding is proved to be a good method for dissimilar welding of medium-thick Al/Cu plates. 相似文献
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This study focuses on the effects of rotational and welding speeds on the microstructure and hardness of joints in friction stir welded single-phase brass. Welds were achieved under low heat input conditions at rotational and welding speeds of 400-800 r/min and 100-300 mm/min, respectively. In order to characterize the obtained welds, optical microscopy and Vickers hardness measurements were taken on the weld cross sections. According to the obtained results, increasing the welding speed and/or decreasing the rotational speed caused the grain size of the stir zone to decrease and, hence, improved the average hardness of this region. These results are discussed with respect to the interplay between the welding parameters and the peak temperature in the weld thermal cycle. 相似文献