Weld shape and microstructure of Ti6Al4V alloy fluoride A-TIG weld

Three types of compounds, i.e. MF type fluorides (including LiF, NaF, KF), MF2 type fluorides (including MgF2, CaF2, BaF2) and KN type potassium (including KF, KCl, KBr), were chosen as activated fluxes to evaluate the effect of weld shape, penetration and microstructure on the A-TIG Ti6Al4V alloy weld. The results show that good appearance and defect-free welded joints could be obtained with fluoride fluxes, except MgF2. Fluorides might act as antioxidants, which could keep weld bead from oxidation. In addition, bead width was significantly decreased in A-TIG with KF flux and MF2 type fluxes. Fluoride could effectively increase weld penetration than other halides (chloride and bromide) under the condition of same cationic. The KF fluoride in MF type had the greatest impact in increasing penetration, while MgF2 fluoride in MF2 type had the highest impact with larger penetration than that with KF fluoride. Furthermore, the solidification microstructure consisted of coarse and columnar grains throughout the complete fusion zone in both TIG and A-TIG welds. And the grains exhibited obvious refining effect in A-TIG weld, but it did not change the phase structure of weld bead.