Microstructurai characterization of electron beam welded joints of TiAl-based intermetallic compound

The feasibility to use electron beam welding to join the nominal composition Ti-48Al-2Cr-2Nb (at.%) alloy was assessed. The microstructure characterization and cracking susceptibility of the joints were evaluated by means of OM,SEM, XRD, and microhardness. It was found that the welded microstructure exhibited columnar and dendritic structures.Microstructural constituents in the fusion zone were a massive gamma structure and some amount of lamellar structure consisting of alternating platelets of α2 and γ. The major contributing factor to the susceptibility to solidification cracking was microsturctural change in this study for the suppression of α phase decomposition leading to produce more retained α2 britfie phase. Compared with transgranular cleavage fracture in the base metal, the weld metal exhibited mainly translamellar fracture.