AZ31B镁合金FSW接头与MIG接头性能对比研究

采用FSW和MIG焊接方法对AZ31B变形镁合金进行焊接试验。结果表明:FSW接头的焊核区受摩擦热、机械搅拌和热塑流动的综合作用,形成粒度细小、晶界明显的等轴再结晶晶粒,平均直径约为5μm;MIG接头的焊缝区在电弧的高温热作用和急速冷却作用下,形成晶界明显的等轴晶,平均尺寸约为20μm;FSW焊接接头力学特性优于MIG,平均抗拉强度达到249.8 MPa,为母材抗拉强度的96.1%,平均伸长率为11.6%;两种接头的断裂面与拉伸方向的夹角约为45°,FSW接头断裂位置在热影响区,断面上有尺寸相差很大的韧窝,而MIG多出现在焊缝区,断面上有韧窝和撕裂棱。

Performance of FSW and MIG weld joints of AZ31B magnesium alloy

Welding experiments of FSW and MIG of AZ31B magnesium alloy were completed. The experimental results show that the equiaxed recrystallized grains of small particle and grain boundary are formed in the WNZ of FSW joint under the comprehensive effect of friction heat,mechanical agitation and thermoplastic flow,the average grain diameter is about 5 μm; equiaxed grains with obvious boundary are formed in the WZ of MIG joint due to the high temperature heat effect and the rapid cooling effect of the arc,and the average grain diameter is about 20 μm. Mechanical properties of FSW joint are higher than those of the MIG joint,the average tensile strength is 249.8 MPa,reaching 96.1% of the tensile strength of base metal and average elongation is 11.6%. The angle between the fracture surface and tensile direction of two kinds of welded joint is approximately 45°. The fracture locates in the heat affected zone for FSW joint,there are dimples on the fracture surface; fracture occurs in the weld zone for MIG joint,dimple and tearing edges appear on fracture surface.