铝合金搅拌摩擦焊缝和母材疲劳裂纹扩展行为

发布时间：2018-06-04 01:03

本文选题：搅拌摩擦焊 + -T和LCCS铝合金　；参考：《航空材料学报》2017年05期

【摘要】：对7075-T6和LC4CS两种铝合金搅拌摩擦焊缝的疲劳裂纹扩展(da/d N)行为进行实验研究,并与7075-T6母材疲劳性能进行对比分析。结果表明:沿焊缝中心、前进和后退边方向,7075-T6搅拌摩擦焊疲劳裂纹扩展速率da/d N均低于LC4CS的da/d N;但沿垂直于焊缝方向两者da/d N基本一致;同种材料焊缝中心da/d N为最低,其次是后退边和前进边,而沿垂直焊缝方向da/d N为最高;7075-T6焊缝中心da/d N与其母材比较,低载荷ΔK下焊缝中心的da/d N较低、但高ΔK下母材的da/d N较低;在前进边、后退边和母材区域疲劳裂纹断口形貌明显不同,在母材区域可以观察到典型的疲劳条纹特征;但沿焊缝中心(焊核)的疲劳裂纹断口,没有任何疲劳条纹特征;7075-T6搅拌摩擦焊缝比LC4CS焊缝具有更好的抗疲劳裂纹扩展阻力,在高ΔK载荷下搅拌摩擦焊核区细小等轴晶粒不能提高疲劳裂纹扩展阻力。
[Abstract]:The fatigue crack propagation (da/d N) behavior of two kinds of aluminum alloy friction stir welds of 7075-T6 and LC4CS is studied and compared with the fatigue performance of 7075-T6 parent material. The results show that the fatigue crack propagation rate da/d N of 7075-T6 friction welding is lower than LC4CS da/d N along the center of the weld, and the fatigue crack growth rate of 7075-T6 friction stir welding is lower than that of LC4CS. In the weld direction both da/d N is basically the same; the same material weld center da/d N is the lowest, followed by the back and forward edges, and the da/d N along the vertical weld line is the highest; the 7075-T6 weld center da/d N is compared with its parent, and the da/d N in the weld center under the low load Delta K is lower. The fatigue crack morphology of the fatigue crack in the parent material region is obviously different, and the typical fatigue stripe can be observed in the parent material area, but there is no fatigue stripe along the fatigue crack fracture along the weld center (weld core), and the 7075-T6 friction weld has better fatigue crack growth resistance than the LC4CS weld and stirred friction under high Delta K load. The small equiaxed grains in the nugget zone can not improve the fatigue crack growth resistance.
【作者单位】：天津大学理学院;天津大学材料科学与工程学院;
【基金】：国家自然科学基金(50775159)
【分类号】：TG457.19

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