Effect of REO (RE = La, Ce) fluxes on A-TIG welding of Ti6Al4V.

The effect of REO (RE = La, Ce) fluxes on penetration and microstructure in 3-mm-thick Ti6Al4V weld joints made by activated flux tungsten inert gas (A-TIG) welding process was investigated. The mechanism of penetration increase was discussed. Microstructure characterization in the fusion zone region was also observed under optical microscope. It is shown that REO fluxes can effectively increase weld penetration of Ti6Al4V for applying a thin layer paste when welding. The mechanism would comply with changing the Marangoni convection in the weld pool, rather than the arc. A-TIG welding with REO fluxes can slightly refine the width of β-Ti grains. Phase constitution shows single α′-Ti in solidification structure in both two welding process. There are no significant changes in weld metal microstructure with and without ReO fluxes. Microhardness distribution of weld seam indicates that the appearance of REO has not affected the metal plastic deformation capacity. [ABSTRACT FROM AUTHOR]