摘要
2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone （PMZ）. Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.
采用单面两层钨极氩弧焊工艺焊接2219-T8铝合金。接头横向拉伸时断裂发生在部分熔化区(PMZ)。针对PMZ组织对接头拉伸断裂行为的影响进行系统研究。PMZ中靠近熔合线的位置晶界共晶较连续,随着距离熔合线距离的增加,晶界共晶的连续程度逐渐降低。断口形貌和接头显微硬度分布表明PMZ是一种梯度材料。其梯度变化的力学性能对接头的断裂行为有重要影响。研究发现,裂纹在靠近正面焊趾的PMZ启裂,启裂后沿远离熔合线的方向扩展,当裂纹尖端扩展到塑性较好的PMZ时,裂纹尖端钝化,随后接头余下部分以剪切形式发生断裂。
