采用超声冲击处理方法对2A12铝合金焊接接头进行全覆盖强化处理.通过弯曲疲劳对比试验,建立了未处理与超声冲击强化处理铝合金焊接接头试样的S-N曲线,分析了超声冲击处理对铝合金焊接接头疲劳性能的影响;通过接头组织、残余应力和断口形貌分析了超声冲击处理提高铝合金焊接接头抗疲劳断裂性能的微观机理.结果表明,超声冲击处理使2A12铝合金焊接接头疲劳强度由40.5MPa提高到56.1MPa,提高了38.5%,同时,接头表层晶粒大幅细化、缺陷减少、组织更加致密,而且引入了最大约为-285MPa的残余压应力.%2A12 aluminum alloy welded joint was full coverage strengthened by ultrasonic impact treatment (UIT). The S-N curves of welded joint samples with and without UIT were set up by making bending fatigue test. The effect of UIT on fatigue properties of aluminum alloy welded joint was analyzed. The fatigue fracture mechanisms of these samples with and without UIT were studied by microstructure, residual stress and fracture surface analysis. The results showed that the fatigue limit of 2A12 aluminum alloy butt-welded joints was increased 38.5％. At the same time, the surface defects of welded joints were reduced substantially after ultrasonic impact treatment. The coarse-grained microstructures of top-surface layer of welded joint were refined after the UIT. The metallurgical structure of the near surface material of the joint was thus density. Compressive residual stress was induced at the surface of welded joints by UIT.
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