Microstructure and crack sensitivity of electron beam welded titanium aluminide joints
(1.State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China2.黑龙江省哈尔滨市哈尔滨工业大学现代焊接生产技术国家重点实验室)
Abstract: Microstructural characterization and crack formed mechanism during electron beam welding of titanium aluminide Ti-45Al-1.7Cr-1.7Nb were investigated. The results show that the welded microstructure exhibits columnar and dendritic structure. Microstructural constituents in the fusion zone are a massive gamma structure and some lamellar structure consists of alternating platelets of α2 and γ. The major contributing factor of the susceptibility to solidstate cracking is thermally induced stress. The import role of the suppression of the α phase decomposition, the difference of α2/γ phases thermal expansion coefficient and the lamellar spacing changes of lamellar structure with cooling rate all play effect on the crack forming mechanism.
Key words: crack； titanium aluminide； electron beam welding； microstructure