7050铝合金搅拌摩擦焊接头超高周疲劳性能
Research on ultra-high-cycle fatigue properties of 7050 aluminum alloy FSW welded joints
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摘要: 采用超高周疲劳试验系统研究7050-T7451铝合金搅拌摩擦焊接头的超高周疲劳性能. 试验结果表明，焊接接头在107周次以上仍然会发生疲劳失效，S-N曲线在108周次左右出现转折点，呈折线型下降；通过SEM对超高周疲劳断口形貌进行观察发现，当应力范围较高时，试件的疲劳裂纹往往在表面萌生，随着应力范围的降低，裂纹有亚表面和内部萌生的倾向；裂纹萌生位置取决于表面起裂和内部起裂相互竞争的结果；试件的断裂位置多为焊接接头的热力影响区和热影响区，EBSD和接头硬度的分析结果表明断裂位置与接头组织不均匀密切相关.
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关键词:
- 铝合金|搅拌摩擦焊|超高周疲劳|断裂位置
Abstract: Ultra high cycle fatigue tests were used to test the fatigue property of 7050 aluminum alloy friction stir welding joint in the very high cycle regime. The results show that fracture still occurs in the welded joints after 107 cycles, and the S-N curves present multi-stage decreasing shapes with the turning point at about 108 cycles. The fatigue fracture morphology of specimen was observed by scanning electron microscope. It is found that fatigue cracks always initiated at the surface under the condition of high stress. However, fatigue crack initiation sites were inclined to transform from surface to subsurface or interior as cyclic loading decreased. The actual initiation sites depend on the competition mechanism of crack initiation from surface, subsurface or interior. Most of the specimens fractured at thermo- mechanical affected zone (TMAZ) and heat affected zone(HAZ). The fracture location is closely related to inhomogeneous microstructure of FSW joint through the EBSD and hardness analysis . -
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