通过高温拉伸试验研究Ti-6Al-4V(TC4)合金激光焊缝的纵向超塑性变形行为,采用扫描电镜观察超塑性变形前后焊缝的显微组织.结果表明:TC4钛合金激光焊缝具有良好的超塑性变形能力,在900 ℃、10~(-3) s~(-1)工艺条件下伸长率达到最大值397%;在超塑性变形过程中,原始焊缝的针状马氏体首先转变为片层状的α+β组织,而后片层组织发生再结晶等轴化;随着变形温度升高或应变速率降低,等轴化程度增大.
The superplastic deformation behavior of laser welded Ti-6Al-4V alloy by hot tensile tests were investigated, and the microstructures of the weld bead before and after superplastic deformation were observed by scanning electron microscopy (SEM). The results show that the laser welded TC4 joint has good superplasticity, and the maximal elongation of 397% is obtained at 900 ℃ and 10~(-3) s~(-1). During the superplastic deformation, the initial acicular martensite transforms into lamellar α+β phases. Then, dynamic recrystallization occurs and the grain expresses equiaxed trend. The equiaxed degree increases with increasing tensile temperature and decreasing strain rate.
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