6005A铝合金自动MIG焊接头疲劳性能的研究

Study on Fatigue Performance of 6005A Aluminum Alloy Automatic MIG Welded Joint

采用自动MIG焊焊接6005A-T6铝合金。使用高频疲劳试验机对焊接接头的疲劳性能进行测试,绘制了S-N曲线,测定其疲劳极限,并对接头的疲劳断口和显微组织进行了分析,研究疲劳断裂的原因。结果表明:6005A铝合金接头的高周疲劳极限应力为105 MPa,S-N曲线拟合公式为σ_(max)=16167N_f^(-0.383);高应力状态的疲劳断口与静态拉伸断口相似,疲劳裂纹萌发区存在缺陷,在疲劳裂纹扩展区未发现呈放射性的扩展辉纹;低应力状态的断口疲劳也萌发于缺陷处,但存在大量扩展辉纹。焊缝组织较为均匀,但是热影响区的粗晶区和焊缝区晶界聚集的第二相对疲劳性能不利。

The 6005A-T6 aluminum alloy was welded by automatic MIG welding. The fatigue performance of the welded joint was tested by using the high frequency fatigue testing machine, the S-N curve was also drawn, and the fatigue limit was determined. The fatigue fracture and microstructure of the welded joint were analyzed to study the causes of fatigue fracture. The results show that the high cycle fatigue limit stress of 6005A aluminum alloy is 105 MPa, and the fitting equation of S-N curve is trm^--16167Nf^383. The fatigue fracture under high stress state is similar to static tensile fracture, there are defects in fatigue crack germination area, and no radioactive extended striation is found in the fatigue crack propagation region.The fatigue fracture under low stress state also occurs in the defect area, but there are a large number of extended striation. The weld microstructure is relatively uniform, but the coarse grain zone of heat affected zone and the second phase aggregated in grain boundary of weld zone are deleterious to fatigue performance.