6005A铝合金激光-MIG复合焊接接头超高周疲劳性能试验研究

对18 mm 6005A铝合金厚板进行多层多道激光-MIG复合焊接,采用超声疲劳试验技术对板状焊接接头与母材的超高周疲劳性能进行试验研究。结果表明,焊接接头和母材在10~9循环周次后均会发生疲劳断裂。焊接接头的高周疲劳数据点分散性较大,母材和焊接接头的S-N曲线均呈连续下降趋势,在10~6~10~9周次范围内焊接接头的疲劳强度为母材的50%~80%。对比IIW标准疲劳曲线发现,焊接接头的疲劳性能在N=10~4循环周次下与IIW标准基本一致,在高周范围内表现优于IIW标准。经扫描电镜微观分析发现,焊接接头的裂纹通常萌生在表面气孔处,疲劳裂纹断裂形式为穿晶断裂,主要表现为准解理断裂特征。

Experimental study on the ultrahigh cycle fatigue properties of laser-MIG welded joints of 18 mm 6005A aluminum alloy

The 6005A aluminum alloy plate with the thickness of 18 mm is welded by the multi-pass multi-layer laser-MIG hybrid welding.Ultrahigh cycle fatigue properties of plate welded joints and base metal are studied with ultrasonic fatigue testing technique.The results show that the fatigue fracture of the welded joints and base metal will still occur when the fatigue life is more than 109 cycles.The high cycle fatigue data points of welded joints are relatively dispersed,both of the S-N fatigue curves of welded joint and base metal display a continuous downward trend.In the range of 106～109 cycles,the fatigue strength of welded joint is only 50％ to 80％ of that of the base metal.Compared with the ⅡW standard fatigue curve,the fatigue properties of welded joint are basically consistent with the ⅡW standard at N=104,and the properties are better than the ⅡW standard in the high cycle range.Microscopic analysis of scanning electron microscopy indicates that cracks in welded joints usually occur on the surface porosities,and the fracture form of fatigue crack is transgranular and mainly shows quasi-cleavage characteristics.