2A12铝合金变极性等离子弧穿孔焊缝性能分析

Microstructure and mechanical properties of variable polarity plasma arc keyhole weld of 2A12 aluminum alloy

采用具有辅助压缩孔喷嘴结构的焊枪,在大电流高焊速的焊接工艺下制备了2A12铝合金变极性等离子弧穿孔焊缝,并分析了焊缝的组织和力学性能.由于辅助压缩孔对焊接电弧的压缩,使正面焊缝宽度变窄,背面焊缝宽度增加,并提高了两侧焊缝的余高.焊缝内部以细小的等轴非枝晶结构为主,其强化相以Al2Cu为主,还有少量的S相.Al2Cu的形状及其分布状况决定了焊缝的力学性能,试验表明基体和焊缝的硬度差别不大,焊缝沿中轴线的显微硬度呈马鞍状分布,焊缝内部比较平缓,正反两侧焊缝的硬度分布波动较大.

Variable polarity plasma arc welding,an efficient and cost-efficient welding technology,has been widely applied to aircraft components manufacture,especially aluminum alloy components. Variable polarity plasma arc keyhole weld of2A12 aluminum alloy was conducted by welding torch with assistant nozzles under high welding speed and high heat input,and microstructure and mechanical properties of weld zone was analyzed as well. Due to the compression of assistant nozzles to plasma arc,crown weld is narrowed,however,root weld is broadened; reinforcements of both welds are increased. In the weld,fine equiaxed nondendritic grains are dominate,strengthening phases are with Al2 Cu phases largely and few S phases. Mechanical properties of weld zone are determined by the size and quantity of Al2 Cu. It could be concluded that the difference of hardness between parent metal and weld is little. Furthermore,microhardness distribution curve alongside longitudinal direction of weld is like U-shape,plain in the middle of weld and fluctuating in both sides of the crown and root weld.