Fig. 1. EBSD analysis and XRD pattern of the as-cast TM and TMN alloys: (a) IPF map of TM alloy; (b) phase map of TM alloy; (c) XRD pattern of TM alloy; (d) grain size of TM alloy; (e) IPF map of TMN alloy; (f) phase map of TMN alloy; (g) XRD pattern of TMN alloy; (h) grain size of TMN alloy.

Fig. 2. TEM analysis of the as-cast TM and TMN alloys: (a) TEM image of TM alloy; (b1, b2) elemental distribution of (a); (c, d) SAED patterns of yellow and red squares in (a); (e) enlarged DF-TEM image in the dark-colored region of (a); (f) TEM image of TMN alloy; (g1-g3) elemental distribution of (f); (h, i) SAED patterns of yellow and red squares in (f); (j) enlarged DF-TEM image in the dark-colored region of (f).

Fig. 3. Room-temperature tensile properties of TM and TMN alloys: (a) engineering stress-strain curves; (b) true stress-strain curves; (c) strain hardening rate-true strain curves; (d) comparison of the mechanical properties (yield strength vs. ultimate elongation vs. elastic modulus) between TMN and some other literature data of Ti alloys [40], [41], [42], [43], [44], [45], [46], [47], [48], [49], [50], [51].

Fig. 4. EBSD mappings of TM and TMN alloys after tensile deformation with the strain of 5%: (a) IPF map of TM alloy; (b) KAM map of TM alloy; (c) phase map of TM alloy; (d) BC map of TM alloy; (e) IPF map of TMN alloy; (f) KAM map of TMN alloy; (g) phase map of TMN alloy; (h) BC map of TMN alloy, ({332}<113> twin boundaries are shown as red lines).

Fig. 5. TEM analysis of single β-Ti phase region in TMN alloy after deformation: (a) TEM image of the area for {332}<113>twinning; (b) enlarge TEM image of orange square in (a); (c) SAED patterns from the green cycle in (b); (d)-(f) BF-TEM image in single β-Ti phase region showing the dislocation pinning.

Fig. 6. TEM analysis of β+ω phase regions in TM and TMN alloy after deformation: (a) TEM image of TM alloy; (b) enlarged TEM image of a β+ω phase region; (c) GPA image of orange dashed box in (b); (d) TEM image of TMN alloy; (e) enlarged TEM image of a β+ω phase region; (f) GPA image of orange dashed box in (e).

Fig. 7. Schematic sketches for the deformation behavior of TM and TMN alloys.

Fig. 8. Fluorescence photos of MC3T3-E1 cells cultured on minimum essential medium, TM and TMN alloys for 8 h in (a1-c1) and (a2-c2), and for 24 h in (d1-f1) and (d2-f2); (a1-f1) ×100, (a2-f2) ×200. The cytoskeletons are green and the nuclei are blue: (a1, a2) and (d1, d2) cells control, (b1, b2) and (e1, e2) TM alloy, (c1, c2) and (f1, f2) TMN alloy.

Fig. 9. (a) Proliferation of MC3T3-E1 cells cultured on MEM, TM and TMN alloys for one, two and three days; (b) the relative growth rate of different groups after one, two and three days.