Fracture toughness of electron beam welded Ti6Al4V

Two pass and three pass bead-over-bead (BoB) electron beam weld technique was attempted on Ti6Al4V to improve its Charpy impact and fracture toughness of weld metal portion. Hardness and microstructural studies were also done to support the findings. The hardness values of the weld metals were found to be higher than their base metal counterpart. The weld metal hardness came down when deposited with bead-over-bead technique. Conventional stringer bead welding caused reduction in Charpy impact toughness compared to its base metal counterpart. Bead-over-bead technique improved the notch toughness of weld metals. The fracture toughness values of the weld metals were found to be superior to that of base metal. This is in contrast to the Charpy impact toughness values where the impact toughness of base metal was better than the stringer and bead-over-bead weld metals. The better fracture toughness of weld metals was related to the basket-weave structure compared to the equi-axed structure of base metal. Bead-over-bead technique was found to help in improving the fracture toughness of weld metal further. Overall, the study showed that the bead-over-bead technique improved both notch toughness and fracture toughness of Ti6Al4V electron beam weld metals.