空心铝挤压型材焊合扩口试验失效分析

Failure analysis on flaring test for welding seam of hollow aluminum extrusion profile

通过成分检测、金相测试、横向拉伸测试及扫描电镜观察,对铝合金地板空心挤压型材焊合扩口试验失效的原因进行分析。根据分析结果得出:空心铝挤压型材焊合扩口试验失效的主要原因为焊合位置存在粘结界面,粘结界面与铝合金基体组织不连续。在扩口试验的外力作用下,在粘结界面与铝合金型材组织观察不连续处萌发裂纹,引发扩口试验失效。扩口试验的失效位置与正常位置处的横向拉伸试验的结果表明,抗拉强度、屈服强度下降明显,伸长率降低至2.3%,低于要求值8%;拉伸试样的断口齐平,为典型的脆性断裂。扩口试验失效处横向拉伸断口的宏观形貌表现出层状、不连续现象,通过SEM观察可知,焊合扩口试验失效处无韧窝特征,存在明显的裂纹及空腔。

The failure reasons of flaring test for welding seam of hollow extrusion profile for aluminum alloy floor were analyzed by composition measurement, metallographic, transverse tensile test and SEM observation. The analysis results show that the main failure reason of flaring test for welding seam of hollow aluminum extrusion profile is that there is a bonding interface at the welding seam position, which is not continuous with the matrix structure of aluminum alloy. Under the action of external force in the flaring test, cracks germinate at the discontinuous position of bonding interface and aluminum alloy profile which causes the failure of the flaring test. From the transverse tensile test results of the failure position and the normal position for the flaring test, the tensile strength and yield strength decrease significantly, and the elongation decreases to 2.3%, which is 8% lower than the required value. In addition, the fracture of the tensile specimen is flush, which is typical brittle fracture. However, the macroscopic morphology of the transverse tensile fracture at the failure position in the flaring test shows a layered and discontinuous phenomenon. Through SEM observation, there is no dimple feature at the failure postion in the welding flaring test, and there are obvious cracks and cavities.