β Grain refinement by yttrium addition in Ti-6Al-4V Wire-Arc Additive Manufacturing

•Elemental Y was added to Ti64 during WAAM to study its effect on β grain morphology.•Y additions induced a CET, however, the equiaxed zone was within the remelt region of deposition.•The width of columnar β grains was significantly reduced throughout the build.•Y2O3 particles delineated β dendrites with a previously unreported interconnected morphology.•Analysis of Y2O3 / β boundary misorientations revealed at least 3 orientation relationships present.