1561铝合金MIG焊接头的低周疲劳性能研究

Study on Low Cycle Fatigue Properties of 1561 Aluminum Alloy Welded Joints

采用金属极惰性气体保护焊(MIG)制备了1561铝合金对接接头。在室温下,应变比为0.1和循环频率为3 Hz时进行了焊接接头的低周疲劳试验。讨论了应变幅对疲劳寿命的影响,分析了疲劳断口的特征。结果表明,该焊接接头的低周疲劳寿命随着应变幅的增加而降低。疲劳断口分为3个区域,即裂纹源区、裂纹稳定扩展区和瞬断区。疲劳寿命主要取决于裂纹稳定扩展区的大小,近表面气孔和脆性金属间化合物相是主要的裂纹形核源,因此控制焊接接头中气孔和脆性金属间化合物的形成是提高疲劳寿命的关键。

1561 aluminum alloy butt welded joints were prepared by metal arc gas welding.At room temperature,the low cycle fatigue experiments were performed with the strain ratio of 0.1 and the cyclic frequency of 3 Hz.The effects of the strain amplitude on the fatigue life were discussed.The fatigue fracture features were analyzed.The results show that the low cycle fatigue life of the welded joints decreases with the increase of strain amplitude.The fatigue fracture is divided to three regions of crack initiation zone,crack stable growth zone and transient fracture zone.The fatigue life depends on the area of crack stable growth zone,the blowholes close to the surface and intermetallic compounds are the main crack nucleation sources.Therefore,the control of the formation of blowholes and intermetallic compounds in the welded joints is the key to improve the fatigue life.