Fig. 1. Schematic process of a new operation showing: (a) Ti-46Al-8Nb bar at the center of heating area while Ti-43Al-3Si seed was placed a little distance away from the heating center; (b) lifting up the seed rapidly and the heating power was reduced for a while; (c) rotation after 5 mm of the crystal growth had been accomplished.

Fig. 2. Shape and dimensions of standard tensile specimens (unit: mm).

Fig. 3. Longitudinal microstructures of Ti-43Al-3Si seed materials grew at the rate of (a): 180 mm/h and (b) 5 mm/h.

Fig. 4. Optical microstructures of the Ti-46Al-8Nb PST crystals from a Ti-43Al-3Si seed at the growth rate of 10 mm/h, showing (a) the microstructure of the whole bar; (b) the magnified microstructure around the seed/main body interface; (c, d) the typical microstructure of the main body and (e) the dendrites morphology in the quench zone .

Fig. 5. Optical microstructures of the Ti-46Al-8Nb PST crystals grew at the growth rate of 20 mm/h, showing (a) the microstructure of the beginning; (b) the microstructure of the end part of main body; and (c) the untransformed β dendrites morphology near the quench zone.

Fig. 6. Typical microstructures of the Ti-46Al-8Nb alloy grew at the rate of (a) 30 mm/h and (b) 40 mm/h.

Fig. 7. Schematic process of a new mechanism on seeding procedure showing (a) nucleation and growth of β phase and peritectic α phase nucleating directly from the melt; (b) β/α transformation in heterogeneous nucleation model, (c) lamellar structure after the whole process; (d) appearance of β secondary dendrites and (e) β/α transformation in homogeneous nucleation model and (f) formation of the columnar B2 phase parallel to the growth direction.

Fig. 8. (a) Photo of fractured tensile samples compared with the un-deformed one (top) (b) and engineering stress-strain curves of standard samples.