7050-T7451铝合金型材/板材搅拌摩擦焊接头成形和疲劳性能研究

doi:10.3901/JME.260290

摘要/Abstract

摘要： 采用搅拌摩擦焊对2.8 mm厚7050-T7451高强铝合金的挤压型材和机加板材进行了对接焊，研究旋转速度对焊缝成形的影响，对比优化工艺参数下垂直(LT)与平行焊缝(L)方向接头的疲劳强度和疲劳寿命S-N曲线。结果表明，当旋转速度为200 r/min时，搅拌区(Stir zone,SZ)存在隧道型缺陷；旋转速度为600 r/min和1 000 r/min时，可获得内部无缺陷的接头。SZ上部主要由后退侧(Retreating side,RS)的母材(Base material,BM)组成，中下部则由两种材料交替层叠，形成洋葱环结构。不同旋转速度下，接头横截面硬度呈现“W”型分布，硬度最低区域为机加侧的热影响区(Heat affected zone,HAZ)，且机加侧HAZ的宽度大于挤压型材的HAZ宽度。在疲劳性能方面，LT方向接头的疲劳强度为228.3 MPa，大于L方向接头的213 MPa。疲劳断口特征上，随应力水平的升高，裂纹扩展区的面积减小，瞬时断裂区的面积增加，疲劳寿命减小。LT方向断口更为粗糙，断裂位于机加侧的HAZ，断口韧窝较大，部分呈拉长状，存在部分大尺寸的第二相颗粒；L方向疲劳断口较为光滑，存在大量细小的韧窝，且韧窝中存在细小的第二相颗粒。

关键词: 搅拌摩擦焊, 7050-T7451高强铝合金, 焊缝成形, 疲劳性能

Abstract: Friction stir welding was used to butt-weld 2.8 mm thick 7050-T7451 high-strength aluminum alloy extruded profiles and machined plates. The influence of rotational speed on weld formation was studied, and the fatigue strength and S-N curves of joints in the vertical (LT) and parallel (L) directions relative to the weld, under optimized process parameters, were compared. The results show that at a rotational speed of 200 r/min, tunnel-type defects occur in the stir zone(SZ); however, defect-free joints are obtained at 600 r/min and 1 000 r/min. The upper part of the SZ primarily consists of base material(BM) from the retreating side(RS), while the middle and lower parts form an onion-ring structure through the alternate lamination of the two materials. Across different rotational speeds, the hardness distribution across the joint cross-section exhibits a “W” shape, with the lowest hardness located in the heat-affected zone(HAZ) on the machining side, which is wider than the HAZ in the extruded profile. Regarding fatigue performance, the LT-direction joint exhibits a fatigue strength of 228.3 MPa, exceeding the L-direction joint’s strength of 213 MPa. In terms of fatigue fracture characteristics, increasing stress levels correlate with a decrease in the crack propagation zone area, an increase in the instantaneous fracture zone area, and a reduction in fatigue life. LT-direction fractures are rougher and located in the machining-side HAZ, featuring large dimples (some elongated) and large-sized second-phase particles. In contrast, L-direction fatigue fractures are relatively smooth, displaying numerous small dimples containing small second-phase particles.

Key words: friction stir welding, 7050-T7451 high-strength aluminum alloy, weld formation, fatigue performance

中图分类号:

TG405

牛鹏亮, 陈浩翔, 张兵宪, 黄春平, 余辉, 刘丰刚, 刘奋成. 7050-T7451铝合金型材/板材搅拌摩擦焊接头成形和疲劳性能研究[J]. 机械工程学报, 2026, 62(14): 150-159.

NIU Pengliang, CHEN Haoxiang, ZHANG Bingxian, HUANG Chunping, YU Hui, LIU Fenggang, LIU Fencheng. Study on Formability and Fatigue Performance of Friction Stir Welded Joints in 7050-T7451 Aluminum Alloy Profiles and Sheets[J]. Journal of Mechanical Engineering, 2026, 62(14): 150-159.

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http://www.cjmenet.com.cn/CN/Y2026/V62/I14/150

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