A review on solid state welding of Fe and Ti based dissimilar joints

Ti-5Ta-2Nb is a candidate structural material for electrolytic dissolvers handling highly oxidising medium in reprocessing plants of fast breeder reactors. Rest of the vessels and piping in the plant are fabricated using 304L austenitic stainless steel. This necessitated fabrication of a dissimilar joint between Ti-5Ta-2Nb and 304L SS. Joining of Tl and Fe based alloys is a challenge due to limited mutual solubility of Fe and Ti and the tendency to form brittle intermetallic phases. The talk will provide a general overview of the various solid state welding methods that have been tried to achieve good quality joints between Ti and Fe based alloys. In particular evolution of interphase microstructure and microchemistry and interdiffusion behaviour in dissimilar joints fabricated using explosive cladding and friction welding techniques will be compared. Systematic investigations carried out to understand the formation of deformation induced phases in the base materials, their thermal stability, interdiffusion of alloying elements across the dissimilar material interface and consequent changes in interface microstructure and microchemistry will be explained. A general frame work adopted effectively combining both experimental and computational tools to predict the formation of various phases, their relative mole fraction and microchemistry and understand their specific influence on the mechanical property of the joints will be demonstrated. (author)