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Review
. 2018 Mar 29;11(4):519.
doi: 10.3390/ma11040519.

A Review of Selective Laser Melted NiTi Shape Memory Alloy

Zhong Xun Khoo  1 , Yong Liu  2 , Jia An  3 , Chee Kai Chua  4 , Yu Fang Shen  5   6 , Che Nan Kuo  7   8
Affiliations
Review

A Review of Selective Laser Melted NiTi Shape Memory Alloy

Zhong Xun Khoo et al. Materials (Basel). .

Abstract

NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed.

Keywords: 3D printing; 4D printing; NiTi; Selective Laser Melting; additive manufacturing; shape memory alloy.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
SEM images of a sample produced using laser power of (a) 25 W during S1, where it illustrates the extent of melting of the powder particles, followed by (b) 60 W during S2, where it shows that there is no obvious unmelted powder or pore inside of the optimized sample after the second scan.
Figure 2
Figure 2
(a) Stress-strain-temperature curve of the best sample tested. The respective (b) stress-strain curve, (c) strain-temperature, and (d) its derivative curve are presented.
Figure 3
Figure 3
Schematic of the differences in the laser absorptivity and heat conductivity of NiTi materials before and after S1: (a) powder bed or poor-melted sample; (b) optimized sample; and (c) excessively-melted sample.
See this image and copyright information in PMC

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