搅拌摩擦焊AA7075-T651铝合金接头的疲劳裂纹扩展

摘要

The aim of the present work is to evaluate the fatigue crack growth behaviour of 12 mm thick AA 7075-T651 aluminium alloy plates joined by FSW. Fatigue crack growth test was carried out on center cracked tensile (CCT) specimens extracted from the FSW joints and unwelded parent metal. Transverse tensile properties of the unwelded parent metal and welded joints were evaluated. Microstructures of the welded joints were analyzed using optical microscopy and transmission electron microscopy. The scanning electron microscope was used to characterize the fracture surfaces. It was found that the ΔKcr of the welded joint is reduced by 10×10-3 MPa·m1/2 in comparison with the unwelded parent metal. Hence, the fatigue life of the friction stir welded AA 7075-T651aluminium alloy joints is appreciably lower than that of the unwelded parent metal, which is attributed to the dissolution of precipitates in the weld region during friction stir welding.%研究12 mm厚AA7075-T651铝合金板搅拌摩擦焊接头的疲劳裂纹扩展行为。从搅拌摩擦焊接头以及母材中截取试样，对试样进行疲劳裂纹扩展实验。对搅拌摩擦焊接头以及母材的横向拉伸性能进行评估。用光学显微镜和透射电镜分析焊接接头的显微组织。用扫描电镜观察试样的断裂表面。与母材相比，焊接接头的ΔKcr降低了10×10-3 MPa·m1/2。搅拌摩擦焊AA7075-T651接头的疲劳寿命明显低于母材的，其原因可归结于焊缝区的析出相在搅拌摩擦焊接过程中的溶解。