Fabrication of NiTi through additive manufacturing: A review

Abstract

Nickel-titanium (NiTi) is an attractive alloy due to its unique functional properties (i.e., shape memory effect and superelasticity behaviors), low stiffness, biocompatibility, damping characteristics, and corrosion behavior. It is however a hard task to fabricate NiTi parts because of the high reactivity and high ductility of the alloy which results in difficulties in the processing and machining. These challenges altogether have limited the starting form of NiTi devices to simple geometries including rod, wire, bar, tube, sheet, and strip. In recent years, additive manufacturing (AM) techniques have been implemented for the direct production of complex NiTi such as latticebased and hollow structures with the potential use in aerospace and medical applications. It worth noting that due to the relatively higher cost, AM is considered a supplement technique for the existing. This paper provides a comprehensive review of the publications related to the AM techniques of NiTi while highlighting current challenges and methods of solving them. To this end, the properties of conventionally fabricated NiTi are compared with those of AM fabricated alloys. The critical steps toward a successful manufacturing such as powder preparation, optimum laser parameters, and fabrication chamber conditions are explained. The microstructural characteristics and structural defects, the influencing factors on the transformation temperatures, and functional properties of NiTi are highlighted to provide and overview of the influencing factors and possible controlling methods. The mechanical properties such as hardness and wear resistance, compressive behaviors, fatigue characteristics, damping and shock absorption properties are also reported. A case study in the form of using AM as a promising technique to fabricate engineered porous NiTi for the purpose of creating a building block for medical applications is introduced. The paper concludes with a section that summarizes the main findings from the literature and outlines the trend for future research in the AM processing of NiTi.

Influence of processing parameters on the evolution of melt pool, porosity, and microstructures in Ti-6Al-4V alloy parts fabricated by selective laser melting

“…Figure 3b shows a SEM micrograph revealing characteristic micro-dendritic features on the surface of powder particles. This phenomenon occurs due to nucleation and growth of dendrites in the powder particle during slow cooling occurring in atomization process [8]. The top surface of the single line deposits was observed under SEM, and the results are presented in Fig.…”

“…Additive manufacturing technologies offer enhanced design capabilities for geometric freedom that allows producing parts which are otherwise not possible to fabricate with traditional manufacturing processes. There are various additive manufacturing processes such as selective laser melting, direct laser deposition, electron beam melting, wire-feed additive manufacturing, shape deposition modeling, ultrasonic consolidation, binder jetting, and friction freeform fabrication for producing metallic components [1][2][3][4][5][6][7][8]. Titanium alloys are used in several structural applications due to their lower density, high strength to weight ratio, corrosion resistance, and elevated temperature properties [9].…”

First printing of continuous fibers into ceramics

“…Recent advances in the field of additive manufacturing have led to the emergence of the three‐dimensional (3D) printing technology, which provides ideas for solving the manufacture problem of CMCs. 3D printing can theoretically be used for rapid prototyping of complex structures by layer‐by‐layer stacking of materials . It can directly print structures by 3D models, with almost no mechanical processing after molding, thereby simplifying the production process and shortening the production cycle.…”

Nitinol Spinal Vertebrae: A Favorable New Substitute

“…Any exertion of force above Af and below Md temperature results in the austenite/ martensite transformation [50,51] which can withstand a strain change of up to 8%. Martensite return to the previous austenitic shape occurs by unloading the loaded sample [43,52].…”