脉冲电流频率对2219铝合金焊缝组织性能的影响

Effect of pulse current frequency on microstructure and mechanical properties of 2219 aluminum alloy weld joints

采用超快速变换复合高频脉冲方波变极性TIG电弧焊接方法进行2219-T87高强铝合金焊接,研究脉冲方波电流频率对焊缝组织性能的影响.结果表明,加入脉冲方波电流后,焊缝组织明显细化,焊缝区由粗大柱状晶向细小等轴晶转变.当脉冲电流频率达超音频段时,在焊缝中部还存在一种呈带状分布的细小等轴非枝晶组织,并与等轴树枝晶组织交替分布.与未加入脉冲电流相比,当脉冲电流频率为60kHz时,接头抗拉强度和断后伸长率分别增加约17.6%和66%.在一定范围内提高脉冲电流频率,可显著减小焊缝熔合区宽度,改善接头硬度分布,明显提高接头塑性,但对接头强度的影响作用并不明显.

The influence of pulse square-wave current frequency on the microstructure and mechanical properties of 2219 high strength aluminum alloy weld joints was investigated based on a novel ultrafast-convert hybrid pulse current variable polarity gas tungsten arc welding technique.The experimental results showed that comparing with no effect of pulse current,the coarse grains changed to fine equiaxed grains.A kind of finer equiaxed non-dentrites was observed distributing in the form of banding at the weld zone while the pulse current frequency was more than 20 kHz.Mechanical properties of weld joints were improved predominantly at the given pulse frequency of 60 kHz,tensile strength and percentage elongation of weld joints are increased by about 17.6% and 66%,respectively,compared to that of weld joints with no effect of pulse current.At the given pulse current amplitude and pulse duty cycle,with the pulse current frequency in certain range increased,the width of fusion zone obviously decreased and the ductility of welds was improved significantly.However,the variation in tensile strength of weld joints was relatively less sensitive with the increase of pulse current frequency.