Abstract
Nitinol (nickel-titanium or Ni-Ti) is the most utilized shape memory alloy due to its good superelasticity, shape memory effect, low stiffness, damping, biocompatibility, and corrosion resistance. Various material characteristics, such as sensitivity to composition and production thermal gradients, make conventional methods ineffective for the manufacture of high quality complex Nitinol components. These issues can be resolved by modern additive manufacturing (AM) methods which can produce net or near-net shape parts with highly precise and complex Nitinol structures. Compared to Laser Engineered Net Shape (LENS), Selective Laser Melting (SLM) has the benefit of more easily creating a high quality local inert atmosphere which protects chemically-reactive Nitinol powders to a higher degree. In this paper, the most recent publications related to the SLM processing of Nitinol are reviewed to identify the various influential factors involved and process-related issues. It is reported how powder quality and material composition have a significant effect on the produced microstructures and phase transformations. The effect of heat treatments after SLM fabrication on the functional and mechanical properties are noted. Optimization of several operating parameters were found to be critical in fabricating Nitinol parts of high density. The importance of processing parameters and related thermal cooling gradient which are crucial for obtaining the correct phase structure for shape memory capabilities are also presented. The paper concludes by presenting the significant findings and areas of prospective future research in relation to the SLM processing of Nitinol.
Highlights
Shape memory is a unique property of certain metallic and polymeric materials by which they can recover their primary shape after deformation when a thermal or mechanical force is applied
Previously published work related to the Selective Laser Melting (SLM) processing of Nitinol has been reviewed to identify and quantify the influential factors involved, process-related issues, and suggest possible areas to work on
Based on the findings to date, it is clear that additive manufacturing could be used to process Nitinol components with high density and near net shape, requiring very little or no post-processing
Summary
Shape memory is a unique property of certain metallic and polymeric materials by which they can recover their primary shape (programmed shape) after deformation (under temperature or stress conditions) when a thermal or mechanical force is applied This ability of shape-memory materials enables them to be used as functional materials in various engineering applications, such as in sensors and actuators, smart structures, biomedical implants and aerospace components [1,2]. Nitinol has a unique set of functional properties based on a reversible martensitic phase transformation These include shape memory effect, pseudoplasticity (thermal behavior), and pseudoelasticity (mechanical behavior). Most applications of Nitinol in the medical field rely on the superelastic property, whereas the shape memory effect is used in actuators and heat engine applications. Avoiding flaws and undesired porosity (reduces load, initiates crack nucleation/propagation)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
