采用Na2SiF6作为表面活性剂激光焊接TC4钛合金，通过观察焊缝表面，确定了Na2SiF6对TC4钛合金激光焊焊缝表面成形的影响；采用高速摄像技术，观察分析了焊件上方高温光致等离子体形态特征变化；借助光学显微镜观察分析了焊缝熔深和熔宽的变化及微观组织. 结果表明，涂覆Na2SiF6活性剂后TC4钛合金激光焊焊缝表面成形良好，可使焊缝熔深增加约0.8% ~ 12%，焊缝表面熔宽降低约10% ~ 29%，能够有效提高焊缝的深宽比；Na2SiF6活性剂改善了焊缝微观组织的不均匀性，改变了焊缝上部β柱状晶的结晶方向，细化了焊缝的晶粒尺寸和微观组织.
Na2SiF6 was used as surface activating flux for laser welding of TC4 titanium alloy. The effect of Na2SiF6 on TC4 titanium alloy laser welding was determined by observing the weld surface. The morphological characteristics of the high temperature plasma above the workpiece was observed and analyzed by using high-speed digital camera system. The variation of weld depth,width and microstructure were analyzed by optical microscope. The experimental results show that laser weld of TC4 titanium alloy has good appearance with activating flux of Na2SiF6, weld penetration increases by about 0.8%~12%, while weld surface width decrease by about 10%~29%, the depth to width ratio is effectively improved. The inhomogeneity of weld microstructure was improved, and the crystallization direction of βcolumnar crystals on the upper part of the weld was changed, the grain size and microstructure of the weld were refined by Na2SiF6.
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