Fig. 1. Experimental equipment and schematic of welding process

Fig. 2. Cross-sectional morphologies of joints welded under different shielding gases. (a) Nitrogen; (b) argon

Fig. 3. Ti-Al binary phase diagram

Fig. 4. Microstructures of joints welded under different shielding gases. (a) (c)Top area; (b) (d)bottom area

Fig. 5. XRD patterns of joints welded under different shielding gases. (a) Nitrogen; (b) argon

Fig. 6. Elemental distribution in dendrites

Fig. 7. EBSD IPFs (left) and (0001) pole figures (right) of α₂ grains in bottom area of joint welded under nitrogen gas. (a)(b) Total α₂ grains; α₂ grains: (c)(d) group 1, (e)(f) group 2, (g)(h) group 3, (i)(j) group 4

Fig. 8. EBSD IPFs (left) and (0001) pole figures (right) of α₂ grains in joint welded under argon gas. (a)(b) Total α₂ grains; α₂ grains: (c)(d) group 1, 　(e)(f) group 2, (g)(h) group 3, (i)(j) group 4

Fig. 9. EBSD analysis results of α₂ grains in top area of joint welded under nitrogen gas. (a) IPF; (b) (0001) pole figure

Fig. 10. EBSD analysis results of TiN dendrite and α₂ grains. (a) IPF of TiN dendrite and α₂ grains; (b) (111) pole figure of TiN dendrite; (c) (0001) pole figure of α₂ grains

Fig. 11. Schematics of growth mechanism of α phase. (a) Acicular α grains nucleated on β grain boundary; (b) equiaxed α grains grown with TiN dendrites as nucleation cores