Microstructure evolution of electron beam welded joints of Ti-43Al-9V-0.3Y and Ti-6Al-4V alloys

Ti-43Al-9V-0.3Y (at%) and Ti-6Al-4V (at%) alloys were successfully welded by electron beam to investigate the microstructure evolution of the joints. The results showed that the microstructure of the weld is comprised of α₂-Ti₃Al, γ-TiAl, together with a few residual α-TiAl solid solution and B2 phase (ordering by β-TiAl solid solution). The casting structure is formed during the solidification process of the weld, which inevitably causes component segregation in some parts of the joint. In high Al content regions, Al element drives α phase ordering into α₂ phase, and eventually introduces the formation of α/γ or α₂/γ lamellar structures. Conversely, in some regions with low Al content, α phases hardly experience microstructure evolution and thus remains to room temperature.