磁场对厚板Ti-6Al-4V合金窄间隙TIG焊缝组织的影响

Effect of magnetic field on weld structure of large thickness Ti-6Al-4V alloy with narrow-gap TIG welding method

对56 mm厚Ti-6Al-4V合金进行窄间隙磁控电弧TIG焊接,通过金相显微镜对接头各区组织进行对比分析。结果表明:在窄间隙的多层单道焊接中,接头各区的组织、结晶形态及生长方向存在很大差异。焊缝区一次结晶组织为表层焊道上表面的柱状粗大组织及熔合线附近、焊道内部的等轴晶组织。熔合线处,电磁作用提高了平面状结晶前沿及后来形成的等轴晶的稳定性,最终随着磁场强度的增加在熔合线附近逐渐由柱状晶转变为等轴晶。焊缝中心处,磁控电弧作用使得生成的等轴晶稳定性提高,随着磁场强度的增加,等轴晶逐渐单方向伸长,在热传导方向上,即焊缝表层垂直方向生成粗大的柱状晶。

A narrow-gap controlling magnetic field TIG welding experiment was conducted directing at the 56 mm-thickness Ti-6A1-4V titanium alloy. Afterwards, an analysis was taken to compare each weld joint microstructure by means of metallographic microscope. The results show that, during the multilayer single channel of narrow gap welding, the joint microstructure, the crystal structure and the growth orientation significantly differ from each other. The first crystal structure in the weld zone is an equiaxed grain which shows a columnar coarse grain at the top layer of the weld surface and near the bond line and the internal weld. Since the electromagnetic effect improves the stability of fiat crystal and the equiaxed grains appear afterwards, ultimately, there are equiaxed grains translated from coarse columnar grains in the front of bond line with the magnetic field strength increasing. Due to the effect of magnetic controlled arc on improving the stability of equiaxed grains, along with the magnetic field strength increasing, the equiaxed grains gradually extend in a single direction; in the direction of heat conduction, i.e., in the vertical direction of the weld surface, the coarse columnar grains generate.