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Additively Manufactured NiTi Implants

Table 2. Recent researches related to mechanical properties
Mechanical Strategies Results Author (s)
properties
Microhardness Control composition The microhardness of Ni Ti, Ni Ti, and Shiva et al. [107]
50
55
Ni Ti are 380, 440, and 525 HV, respectively.
45
Control AM method The microhardness of SLM-NiTi and Shiva et al. [107]
LENS-NiTi are 540–735 HV and 380 HV,
respectively.
Repetitive scanning strategy Excellent strain hardening effect over 300 Yang et al. [108]
MPa.
Compressive Dense, SC and BCC structure of Dense NiTi can withstand 30.2% compression Andani et al. [113]
strength SLM-NiTi deformation and fail at 1620 MPa. The SC
structure NiTi with a porosity of 58% reached
410 MPa, and it failed after 15.6% compression
deformation. The BCC structure NiTi with
a porosity of 69% reaches 63 MPa and fails
after 10.5% compression deformation.
Use synchrotron radiation-based 6% of the uniaxial compression resulted in up Bormann et al. [112]
micro-CT to evaluate the internal to 15% local compressive strain
displacement and strain field.
Fabricate the biomimetic claw When the applied stress approached 234 MPa, Ma et al. [114]
structure SLM-NiTi the maximum compressive strain was 0.5776.
Tensile strength Stripe width 4 mm and hatch The tensile strain of SLM-NiTi is 15.6%, and Xiong et al. [115]
rotation of 67° the part shows 99% shape memory recovery
under 50% compression deformation.
Manufacturing SLM-NiTi through The tensile strain of SLM-NiTi is 15.2 ± Zhang et al. [124]
stripe rotation scanning strategy 0.8%. After pre-deformation of 4% and 6%,
the recovery rates were 97.7 ± 1.2% and 92.5
± 2.0%, respectively.
SLM-NiTi manufactured in a high Oxygen will destroy the grain boundary layer Wang et al. [119]
oxygen atmosphere (>25 ppm) by layer, eventually destroying the part.
SLM-NiTi produced in three The samples made at 45° relative to the build Bayati et al. [123]
different structural directions plate broke at~600 MPa, while the edge and
flat samples both broke at~350–400 MPa.
Fatigue Manufacturing SLM-NiTi through The fatigue life of the samples manufactured Bayati et al. [123]
behavior stripe rotation scanning strategy at 45° relative to the build plate is the longest,
and the fatigue life of the edge samples is the
shortest.
SLM-NiTi scaffold with three Compared with the traditional octahedron unit Speirs et al. [126]
different unit cells cell structure, TPMS show excellent static
mechanical properties and fatigue life, and
the sheet gyroid structure shows the highest
fatigue life.
Damping Use two sets of SLM parameters to During cooling in a wide temperature Wang et al. [9]
properties produce NiTi to generate alternate range (~130 K), good damping property is
layered austenite/martensite obtained at both low (1 Hz) and high (90 kHz)
structure oscillation frequencies.

5. Conclusions and challenges focuses on influencing factors in SLM production, which
can significantly affect the quality of products. To obtain
This paper reviews the recent developments of AM-NiTi, the required shape memory behavior, the Ni/Ti ratio must
especially SLM-NiTi in biomedical applications. It be precisely controlled. A qualified orthopedic implant

34 International Journal of Bioprinting (2021)–Volume 7, Issue 2