Interfacial bonding mechanism of linear friction welded dissimilar Ti2AlNb–Ti60 joint: Grain intergrowth induced by combined effects of dynamic recrystallization, phase transformation and elemental diffusion

The blisk composed of Ti2AlNb intermetallic alloy and Ti60 titanium alloy with its dual properties is considered as the ideal high-performance component in advanced aeroengines. There are incompatibilities at the interface during welding using conventional fusion techniques like electron beam. In this work, this dissimilar alloy joint was successfully produced employing linear friction welding, and a joint whose strength over that of Ti60 base metal was obtained. The intergrowth bonding mechanism at the interface was promoted by the combined effects of dynamic recrystallization, phase transformation and solute element diffusion. Studies showed that during heating of welding, there were total α2→B2 and O→B2 transformations on the Ti2AlNb side of the interface and α→β transformation at the Ti60 side of the interface, while continuous dynamic recrystallizations of B2 and β phases were taking place. Solute elements, Ti, Al and Nb, diffused at the interface, resulting in recrystallized grains on both sides of the interface achieving intergrowth. During rapid cooling, β→αˊ transformation occurred at the Ti60 side, while B2 phase remained intact on the Ti2AlNb side due its high Nb content, which makes B2/αˊ phase interface develop in intergrowth grain after welding. Due to the strong interfacial bonding strength as a result of intergrowth grains, this joint shows significant advantages compared to other welding techniques, and allows to expand its industrial use.