Table 2.

Recent researches related to mechanical properties

Mechanical properties	Strategies	Results	Author (s)
Microhardness	Control composition	The microhardness of Ni55Ti, Ni50Ti, and Ni45Ti are 380, 440, and 525 HV, respectively.	Shiva et al.[107]
	Control AM method	The microhardness of SLM-NiTi and LENS-NiTi are 540–735 HV and 380 HV, respectively.	Shiva et al.[107]
	Repetitive scanning strategy	Excellent strain hardening effect over 300 MPa.	Yang et al.[108]
Compressive strength	Dense, SC and BCC structure of SLM-NiTi	Dense NiTi can withstand 30.2% compression 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.	Andani et al.[113]
	Use synchrotron radiation-based micro-CT to evaluate the internal displacement and strain field.	6% of the uniaxial compression resulted in up to 15% local compressive strain	Bormann et al.[112]
	Fabricate the biomimetic claw structure SLM-NiTi	When the applied stress approached 234 MPa, the maximum compressive strain was 0.5776.	Ma et al.[114]
Tensile strength	Stripe width 4 mm and hatch rotation of 67°	The tensile strain of SLM-NiTi is 15.6%, and the part shows 99% shape memory recovery under 50% compression deformation.	Xiong et al.[115]
	Manufacturing SLM-NiTi through stripe rotation scanning strategy	The tensile strain of SLM-NiTi is 15.2 ± 0.8%. After pre-deformation of 4% and 6%, the recovery rates were 97.7 ± 1.2% and 92.5 ± 2.0%, respectively.	Zhang et al.[124]
	SLM-NiTi manufactured in a high oxygen atmosphere (>25 ppm)	Oxygen will destroy the grain boundary layer by layer, eventually destroying the part.	Wang et al.[119]
	SLM-NiTi produced in three different structural directions	The samples made at 45° relative to the build plate broke at~600 MPa, while the edge and flat samples both broke at~350–400 MPa.	Bayati et al.[123]
Fatigue behavior	Manufacturing SLM-NiTi through stripe rotation scanning strategy	The fatigue life of the samples manufactured at 45° relative to the build plate is the longest, and the fatigue life of the edge samples is the shortest.	Bayati et al.[123]
	SLM-NiTi scaffold with three different unit cells	Compared with the traditional octahedron unit cell structure, TPMS show excellent static mechanical properties and fatigue life, and the sheet gyroid structure shows the highest fatigue life.	Speirs et al.[126]
Damping properties	Use two sets of SLM parameters to produce NiTi to generate alternate layered austenite/martensite structure	During cooling in a wide temperature range (~130 K), good damping property is obtained at both low (1 Hz) and high (90 kHz) oscillation frequencies.	Wang et al.[9]