Fig. 1. (a) Schematic diagram of l-PBF technique; (b) chessboard scanning strategy, defined building direction (BD) and coordinate axis; (c) cubic samples for parameter optimization; (d) rectangle samples for tensile tests and (e) tensile specimen.

Fig. 2. Characterization of Ti-41Nb pre-alloyed powder: (a) SEM morphology; (b) particle size distribution; (c) XRD pattern of the raw powder; (d-f) backscattered electron (BSE) image and corresponding EDS mapping results.

Fig. 3. (a) Contour map of the relative density of l-PBFed Ti-41Nb alloys with variable quantity containing laser powder and laser scanning velocity; (b) relationship between the energy density and metallurgical quality; (c) surface profile on top surface profile and (d) 3D micro-CT image of the l-PBFed Ti-41Nb alloy under the proper parameter.

Fig. 4. XRD patterns of the CRA and l-PBFed specimens containing vertical and horizontal planes.

Fig. 5. EPMA maps of typical element distribution containing Ti and Nb on horizontal (a, b) and vertical planes (c, d) of l-PBFed Ti-41Nb alloy.

Fig. 6. EBSD inverse pole figure (IPF), grain boundaries (GB) and kernel average misorientation (KAM) of the selected yellow rectangle: (a) horizontal plane of l-PBFed Ti-41Nb alloy; (b) vertical plane of l-PBFed Ti-41Nb alloy; (c) CRA alloy.

Fig. 7. Grain size distribution maps: (a) horizontal plane of l-PBFed Ti-41Nb alloy; (b) vertical plane of l-PBFed Ti-41Nb alloy (width of the columnar grains); (c) CRA alloy.

Fig. 8. SEM microstructures on (a-c) horizontal plane and (d-f) vertical plane of l-PBFed sample and (g-i) RD-TD plane of CRA specimen.

Fig. 9. FE-TEM characterization: (a) bright field TEM images; (b, c) corresponding EDS mapping; (d) SAED along the [-113]β zone axis and (e) corresponding dark-field TEM image recorded using reflection spot marked by the red circle of l-PBFed Ti-41Nb alloy; (f) micrograph and corresponding SAED along the [-113]β zone axis of CRA Ti-41Nb sample.

Fig. 10. Mechanical properties of both l-PBFed and CRA samples: (a) tensile engineering stress-strain curves; (b) histogram of tensile strength and elongation; typical fracture surface of (c) l-PBFed sample and (d) CRA specimen.

Fig. 11. (a) Thermal conductivity and (b) contact angles of CP-Ti and l-PBFed Ti-41Nb samples.

Fig. 12. Fluorescent images of rBMSCs cultured on (a) CP-Ti and (b) l-PBFed Ti-41Nb for 24 h with actin stained with AlexaFluor 546 phalloidin (red) and nucleus stained with DAPI (blue).

Fig. 13. (a) Fluorescent density of alamarblue for rBMSCs cultured on CP-Ti and l-PBFed Ti-41Nb alloys for 1, 4, and 7 days; (b) SEM cell morphologies of rBMSCs cultured on CP-Ti and l-PBFed Ti-41Nb alloys for 1, 4, and 7 days.

Fig. 14. (a) Relative activity of ALP on CP -Ti and l-PBFed Ti-41Nb alloys after cultured for 7 and 14 days (??p < 0.01); (b) ALP positive areas of rBMSCs cultured on CP -Ti and l-PBFed Ti-41Nb alloys for 7 and 14 days.

Fig. 15. Quantitative results of extracellular matrix mineralization on CP-Ti and l-PBFed Ti-41Nb alloys after cultured for 7 and 14 days (??p < 0.01); (b) extracellular matrix mineralization positive areas of rBMSCs cultured on CP-Ti and l-PBFed Ti-41Nb alloys for 7 and 14 days.