The NiTi alloy is widely known for its unique properties which are pseudoelastic and shape memory effect. These two unique properties are suitable for biomedical applications such as an implant, biomedical suture etc. Various methods are available to produce NiTI like Metal Injection Molding (MIM), Vacuum Arc Melting (VAM), additive manufacturing (AM), etc. The most common method is MIM where the specimen undergoes the process of mixing, injection moulding, debinding and sintering. Commonly after sintering process, the specimen is inhomogeneous due to the formation of secondary phases and impurity content. These impurities content can be reduced by applying heat treatment which improves the microstructure of NiTi. The objective of the study is to investigate the effect of heat treatment on the microstructure and phase transformation of NiTi. In this study, samples were fabricated with each 50.0at% and 50.8at% of NiTi composition by using MIM. An annealing heat treatment of 430˚oC was applied to the heat-treated samples for increasing the yield strength of NiTi. All heat-treated samples were subjected to Differential Scanning Calorimetry (DSC) test for analysing the phase transformation; X-Ray Diffraction (XRD) test for identifying the existence of any secondary phases; and Scanning Electron Microscopy (SEM) test for observing the change in the microstructure. The results indicated that upon heating through the annealing process, the secondary phase of martensite which is known as NiTi (B19’) diffused and formed the austenite phase of NiTi (B2). Results from the DSC and SEM analyses showed that the formation of B2 is dominant after the heat treatment process.
This paper highlights the influence of titanium hydride particle on the rheological behaviour of nickel-titanium feedstock used in the metal injection process. The ratio of 50at% nickel and 50at% titanium hydride with 2 different powder loadings (65.5vol% and 67.5vol%) were investigated. A Rosand RH2000 capillary rheometer was used to determine the flow behaviour of feedstocks. The feedstocks were characterized at different temperature ranging from 150°C and 170°C and shear rate ranging from 50/s and 4442.63/s. The results showed on pseudo-elastic behaviour flow of NiTi feedstock which is suitable for injection moulding process.
Introduction: Wettability and fluid absorption are two important bone scaffold characteristics that determine proper cell attachment and flow of nutrition and oxygen. To imitate the human bone structure, the current study was carried to investigate the effect of the porosity of bone scaffold and contact angle of the fluid by evaluating the height of capillary rise. Methods: The structure was simplified based on the circle and square pattern and evaluated using Computational Fluid Dynamic (CFD). Porosity and contact angle were varied from 50% to 80%, while the contact angle ranged from 0 degrees to 60 degrees. The result was evaluated further using statistical analysis. Results: The CFD result was in agreement with Jurin’s law (9% error). The height of capillary rise was found to be excellent for the square pattern, while the circle was found to work across all the investigated parameters better. The porosity was correlated with the height of capillary rise (r = -0.549). The strongest correlation happened to contact angle (r =-0.781). Conclusion: The study concludes that water absorption and wettability can be altered and improved based on porosity. Meanwhile, the height of capillary rise depends strongly on the contact angle.
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