Laser Powder Bed Fusion Process of NiTi Alloys for Orthopedic Implants and Their Superelastic Properties

Xu Zheng; Jun Song; Bo Song; Lei Zhang; Shiyu Zhong; Yan Liu; Yuanjie Zhang; Yusheng Shi

doi:10.3788/CJL250453

Chinese Journal of Lasers, Volume. 52, Issue 12, 1202302(2025)

Laser Powder Bed Fusion Process of NiTi Alloys for Orthopedic Implants and Their Superelastic Properties

Xu Zheng¹, Jun Song¹, Bo Song^1、*, Lei Zhang¹, Shiyu Zhong², Yan Liu¹, Yuanjie Zhang¹, and Yusheng Shi¹

¹State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei , China

²Department of Mechanical Engineering, City University of Hong Kong, Hong Kong 999077,China

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Figures & Tables(13)

Fig. 1. NiTi powder. (a) Surface morphology of NiTi powder under scanning electron microscope; (b) particle size distribution of NiTi powder; (c) DSC curves of NiTi powder

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Fig. 2. Effects of laser power and scanning speed on phase transition temperature and relative density of LPBF formed NiTi alloy.

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Fig. 3. Changes in phase transition temperature and relative density of sample at P=250 W. (a) DSC curves; (b) trend of phase transition temperature; (c) trend of porosity; (d) surface morphology of the alloy under OM

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Fig. 4. XRD patterns of NiTi alloy powder and samples

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Fig. 5. IPFs, KAM maps, and grain distributions of NiTi alloy. (a)‒(c) 1# sample; (d)‒(f) 2# sample; (g)‒(i) 3# sample

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Fig. 6. Tensile stress-strain curves of samples under different scanning speeds when P=250 W

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$Morphologies and local magnification views of tensile fractures under SEM. (a)‒(c) 1# sample; (d)‒(f) 2# sample; (g)‒(i) 3# sample$

Fig. 7. Morphologies and local magnification views of tensile fractures under SEM. (a)‒(c) 1# sample; (d)‒(f) 2# sample; (g)‒(i) 3# sample

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Fig. 8. Cyclic tensile curves of different samples when σ_max=420 MPa. (a)(b) 1# sample; (c)(d) 2# sample; (e)(f) 3# sample

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Fig. 9. Curves of recovery strain and deformation recovery rate for each cycle. (a) Recovery strain; (b) deformation recovery rate

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Fig. 10. Comparison of superelastic properties of NiTi alloy

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Table 1. Detailed printing parameters during LPBF

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Table 1. Detailed printing parameters during LPBF

Parameter	Value
Laser power P /W	190，220，250，280，310
Laser scanning speed v /（mm·s^-1）	900，1000，1100，1200，1300
Hatch distance H /μm	110
Powder layer thickness t /μm	40
Energy density E_v /（J·mm^-3）	30‒80

Table 2. Tensile properties of NiTi alloys fabricated by LPBF (P=250 W)
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Table 2. Tensile properties of NiTi alloys fabricated by LPBF (P=250 W)
Sample
No.
v /
（mm·s^-1）
UTS /
MPa
YS /
MPa
EL /
%
1# 900 466.4 306.0 12.20
2# 1100 625.6 336.8 14.67
3# 1300 430.7 285.5 12.17

Table 3. 1^st and 10^th cycle responses of superelasticity of NiTi alloy fabricated by LPBF
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Table 3. 1^st and 10^th cycle responses of superelasticity of NiTi alloy fabricated by LPBF
Sample No. v /（mm·s^-1） 1^st cycle 10^th cycle
ε_tot /% ε_rec/% η /% ε_tot /% ε_rec /% η /%
1# 900 10.09 9.38 92.98 8.97 6.21 99.46
2# 1100 5.05 4.75 94.02 4.72 3.22 99.51
3# 1300 9.43 8.54 90.57 6.85 4.79 99.51

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Xu Zheng, Jun Song, Bo Song, Lei Zhang, Shiyu Zhong, Yan Liu, Yuanjie Zhang, Yusheng Shi. Laser Powder Bed Fusion Process of NiTi Alloys for Orthopedic Implants and Their Superelastic Properties[J]. Chinese Journal of Lasers, 2025, 52(12): 1202302

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