Electrochemical Corrosion Behavior of Laser Gas Nitrided Layer on the NiTi Shape Memory Alloy in Hank’s Solution

2011 ◽  
Vol 299-300 ◽  
pp. 179-182
Author(s):  
Song Zhang ◽  
Hu Jiao Tang ◽  
Fang Hu ◽  
Chun Hua Zhang ◽  
Hau Chung Man ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Continuous Wave ◽  
Nitrided Layer ◽  
Electrochemical Corrosion ◽  
Corrosion Current ◽  
Optimum Process ◽  
Niti Shape Memory Alloy ◽  
Niti Sma ◽  
Electrochemical Corrosion Behavior

A nitrided layer was formed on the NiTi shape memory alloy (SMA) after being irradiated by a continuous wave Nd-YAG laser in a N2 environment. With optimum process parameters, a compact laser modified gradient layer reinforced with fine TiN particles was achieved. Electrochemical measurements of the laser gas nitrided layer on the NiTi SMA showed that the corrosion potential and the breakdown potential were increased while the corrosion current was decreased as compared with the untreated the NiTi SMA. The polarization resistance of the laser gas nitrided layer on the NiTi SMA was increased significantly while the capacitance was decreased. Based on the EIS spectra, a simple model and an equivalent circuit were proposed to describe the electrode-electrolyte interfaces.

Electrochemical Deposition of Apatite/Collagen Composite Coating on NiTi Shape Memory Alloy and Coating Properties

2009 ◽  
Vol 1239 ◽  
Author(s):  
Min Wang ◽  
Tao Sun
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Coating ◽  
Electrochemical Deposition ◽  
Composite Coatings ◽  
Surface Characteristics ◽  
Corrosion Current ◽  
Niti Shape Memory Alloy ◽  
Niti Sma ◽  
Transmission Electron

AbstractIn this investigation, an apatite/collagen composite coating was formed at 37C on a NiTi shape memory alloy (SMA) through electrochemical deposition using double-strength simulated body fluid (2SBF) which contained dissolved collagen. Surface characteristics, wettability and stability of the composite coating were subsequently studied. Scanning electron microscope (SEM) examination of the surface of composite coatings revealed that many collagen fibers were embedded in apatite with flake-like structure and apatite nanocrystals nucleated and grew on collagen fibrils. Energy dispersive X-ray (EDX) spectroscopy analysis showed that the Ca : P ratio of the composite coating was about 1.35, which is close to that of octocalcium phosphate. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) analysis were also conducted for the composite coating. Compared to bare NiTi SMA samples, the potentiodynamic polarization curves of NiTi SMA samples with the composite coating displayed lower corrosion current density, more positive corrosion and breakdown potential, suggesting that the composite coating was chemically stable and provided corrosion resistance for NiTi SMA.

EFFECTS OF PARTICLE SIZE AND SINTERING TEMPERATURE ON SUPERELASTICITY BEHAVIOR OF NiTi SHAPE MEMORY ALLOY USING NANOINDENTATION

2021 ◽  
pp. 2150024
Author(s):  
C. VELMURUGAN ◽  
V. SENTHILKUMAR
Keyword(s):  
Particle Size ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Sintering Temperature ◽  
Niti Alloy ◽  
Indentation Load ◽  
Niti Shape Memory Alloy ◽  
Recovery Ratio ◽  
Work Recovery ◽  
Niti Sma

The present study investigates the superelasticity properties of spark plasma sintered (SPS) nickel titanium shape memory alloy (NiTi SMA) with the influence of sintering temperature and particle size. The nanoindentation is conducted on the surface of the NiTi SMA at various loads such as 100, 300 and 500[Formula: see text]mN. The nanoindentation technique determines the quantitative results of elasto-plastic properties such as depth recovery in the form of superelasticity, stiffness, hardness and work recovery ratio from load–depth ([Formula: see text]–[Formula: see text]) data during loading and unloading of the indenter. Experimental findings show that the depth and work recovery ratio increases with the decrease of indentation load and particle size. In contrast, increasing the sintering temperature exhibited a better depth and work recovery due to the removal of pores which could enhance the reverse transformation. The contact stiffness is influenced by [Formula: see text] which leads to attain a maximum stiffness at the highest load (500[Formula: see text]mN) and particle size (45[Formula: see text][Formula: see text]m) along with the lowest sintering temperature (700∘C). NiTi alloy exhibited a maximum hardness of 9.46[Formula: see text]GPa when subjected to indent at the lowest load and particle size sintered at 800∘C. The present study reveals a better superelastic behavior in NiTi SMA by reducing the particle size and indentation load associated with the enhancement of sintering temperature.

Fabrication of an Apatite/Collagen Composite Coating on the NiTi Shape Memory Alloy through Electrochemical Deposition and Coating Characterisation

2009 ◽  
Vol 618-619 ◽  
pp. 319-323 ◽  
Author(s):  
Parama Chakraborty Banerjee ◽  
Tao Sun ◽  
Jonathan H.W. Wong ◽  
Min Wang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Composite Coating ◽  
Electrochemical Deposition ◽  
Room Temperature ◽  
Composite Coatings ◽  
Deposition Process ◽  
Niti Shape Memory Alloy ◽  
X Ray ◽  
Niti Sma

To improve the biocompatibility and bioactivity of NiTi shape memory alloy (SMA), apatite/collagen composite coatings were fabricated on the surface of NiTi SMA at room temperature using the electrochemical deposition technique. Spherical apatite particles and fibrous collagen that formed the composite coating were visible under scanning electron microscope (SEM). The Ca/P ratio of the apatite component in the coating, as determined by energy dispersive X-ray spectroscopy (EDX), was about 1.38 which is slightly higher than that of octocalcium phosphate (OCP). X-ray diffraction result showed that the apatite was amorphous, which was due to the low temperature (i.e., room temperature) deposition process. The structure of the composite coatings was further characterized using Fourier transform infrared reflection spectroscopy (FTIR). It was also found that, compared to bare NiTi SMA samples, the wettability of as-deposited samples was increased because of the formation of the composite coating.

Characterization of Anatase Coatings on NiTi Shape Memory Alloy by Plasma Electrolytic Oxidation Method

2011 ◽  
Vol 121-126 ◽  
pp. 3837-3841
Author(s):  
Li Hong Lu ◽  
Jing Wu Zhang ◽  
De Jiu Shen
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Plasma Electrolytic Oxidation ◽  
Niti Shape Memory Alloy ◽  
Aqua Regia ◽  
X Ray ◽  
Niti Sma ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Peo Coatings

The anatase coatings was obtained by aqua regia dealloying and plasma electrolytic oxidation (PEO) method on NiTi shape memory alloy (SMA) substrate. The PEO manufacturability of NiTi SMA before and after dealloying was researched. The PEO surface morphologies of the aqua regia treated and untreated specimens were investigated with scanning electron microscopy (SEM). The composition of the PEO coatings was investigated with X-ray diffraction (XRD). The element concentration of the surface of the PEO-treated NiTi SMA was measured by an energy dispersive X-ray spectrometer (EDS). The results indicate that the pre-treatment technology by aqua regia dealloying can greatly improve the PEO manufacturability and the PEO morphologies of the NiTi SMA. The optimum dealloying parameters are at room temperature for 10 min. At this circumstance, the PEO manufacturability of the treated samples is most close to that of the industrial pure titanium. There are many honeycomb-like micro-pores in the surface of the PEO coatings, which act as discharging channels. The cracks are invisible in the SEM images of the PEO coatings. The PEO coatings formed on the NiTi is composed of Ti, Ni, Al, O, Au and P. The composition of the PEO coatings is mainly composed of NiTi phase and anatase phase.

Thermal Parameters Influence Assessed by Electrochemical Impedance Spectroscopy on a Ni50Ti48Nb2 Shape Memory Alloy

2018 ◽  
Vol 69 (1) ◽  
pp. 86-90 ◽  
Author(s):  
Ioana Arina Gherghescu ◽  
Daniela Ionita ◽  
Sorin Ciuca ◽  
Ruxandra Elena Dumitrescu
Keyword(s):  
Corrosion Resistance ◽  
Electrochemical Impedance Spectroscopy ◽  
Impedance Spectroscopy ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Electrochemical Corrosion ◽  
Transformation Temperatures ◽  
Electrochemical Corrosion Behavior

This paper presents some electrochemical impedance spectroscopy research results concerning the corrosion resistance of a shape memory Ni50Ti48Nb2 alloy. This one was previously studied by SEM and DSC [1,2] but some new research features had to be made clear in order to be able to explain its electrochemical corrosion behavior. The chemical composition Ni50Ti48Nb2 was chosen in order to obtain a shape memory alloy having a wider hysteresis than equiatomic NiTi, for the purpose of achieving a better thermomechanical stability. Cryogenic applications are aimed. After processing the cast ingot, two samples, S1 and S2, were further annealed at 800�C/12 h and, respectively, at 900�C/12h. Scanning electron micrographs together with the chemical elements mapping results were obtained. They were related to the previous results concerning the informations on the structure of the different phases found in this NiTiNb alloy: austenite, martensite and secondary phases, as well as some primary compounds [1,2]. Considering the size and shape of the complex precipitate particles of NiTiNb in the two differently heat treated samples, these were found responsible for some changes in the transformation temperatures [3] but the electrochemical corrosion behavior of the alloy seems to be influenced to a lesser extent by the heat treatments. Both samples exhibit good values of corrosion resistance, however S2 shows better values than S1. Thus lower transformation temperatures and a slightly better corrosion resistance make the Ni50Ti48Nb2 alloy annealed at 900�C/12h subsequently submitted to thermal cycling to be the right choice for producing couplings in the cryogenic industry.

The fabrication of NiTi shape memory alloy by selective laser melting: a review

2019 ◽  
Vol 25 (8) ◽  
pp. 1421-1432 ◽  
Author(s):  
Xizhang Chen ◽  
Kun Liu ◽  
Wei Guo ◽  
Namrata Gangil ◽  
Arshad Noor Siddiquee ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Selective Laser Melting ◽  
Process Analysis ◽  
Research Direction ◽  
Process Equipment ◽  
Niti Shape Memory Alloy ◽  
Laser Melting ◽  
Content Type ◽  
Niti Sma

Purpose In recent years, the use of high performing materials, and application of additive manufacturing technology for industrial production has witnessed a steady rise and its expanse is only to increase in the future. “Selective laser melting (SLM) technique” for an exotic nickel-titanium (NiTi) shape memory alloy (SMA) is expected to a great facilitator to research in this area. The purpose of this paper is to put forth the research direction of NiTi shape memory alloy by selective laser melting. Design/methodology/approach This review also summaries and skims out the information on process equipment, adopted methodologies/strategies, effects of process parameters on important responses e.g. microstructure and comprehensive functional and mechanical properties of SLM-NiTi. In particular, the functional characteristics (i.e. shape memory effects and super-elasticity behavior), process analysis and application status are discussed. Findings Current progresses and challenges in fabricating NiTi-SMA of SLM technology are presented. Practical implications This review is a useful tool for professional and researchers with an interest in the field of SLM of NiTi-SMA. Originality/value This review provides a comprehensive review of the publications related to the SLM techniques of NiTi-SMA while highlighting current challenges and methods of solving them.

Mechanical Characterisation of the NiTi Shape Memory Alloy for Microfluidic Valve Applications

2013 ◽  
Vol 1581 ◽  
Author(s):  
Alistair M. Waddell ◽  
Jeff Punch ◽  
Walter Stanley ◽  
Nicholas Jeffers ◽  
Jason Stafford
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
High Stress ◽  
Thermal Control ◽  
Telecommunications Industry ◽  
Image Correlation ◽  
Niti Shape Memory Alloy ◽  
Valuable Insight ◽  
Laser Array ◽  
Niti Sma

ABSTRACTPhotonics Integrated Circuits (PICs) are being applied by the telecommunications industry as transceivers for fibre optic networks. The core component of a typical PIC is the laser array and these devices can have relatively low operating temperatures (15°C - 25°C) with a tight operating range (±0.1K). To accommodate such a specification, a thermal control system is required that can change the cooling rate through feedback. The power density of next generation PICs is at such a level to demand novel thermal management architectures including developments such as near source liquid cooling. In order to control the thermal performance of fluidic devices, effective methods for varying the rate of coolant are an essential component. Consequently, micro-valve structures are required, ideally involving passive actuation to meet stringent reliability standards. One solution to this challenge is to exploit the phase-change driven shape memory effect of the NiTi Shape Memory Alloy (SMA). A micro-valve could be developed from the NiTi SMA, thermally coupled to the laser array component in order to work passively to regulate the flow of coolant in a micro-channel. Such a valve would have to be intrinsically reliable, and the goal of this paper is to investigate the conditions that will affect this reliability. The objective of the work is to investigate the mechanical properties relevant to the design of a passive NiTi SMA micro-valve, with a focus on the formation of stress-induced Martensite bands. It is not understood why these bands form on a plane inclined at ∼55° to the axis of loading and in this paper theory is presented that suggests a reasoning for this. A plate sample of NiTi was tested in uni-axial tension and Digital Image Correlation (DIC) used to analyse the strain fields across the surface of the sample. The DIC results revealed areas of high stress concentrations occurring in bands inclined on average 53.86° to the axis of loading. The theory and experimental observations are in agreement with the literature but to validate the theory the crystal texture needs to be analysed in the stress concentration regions. This paper provides valuable insight into the mechanical behaviour of a passive NiTi SMA micro-valve subjected to a sufficient pressure to form stress-induced Martensite.

Crack Closure and Shape Restoration Using NiTi Shape-Memory Alloy

2011 ◽  
Vol 261-263 ◽  
pp. 721-724
Author(s):  
Li Sun ◽  
Wei Min Huang ◽  
Chuan Kai Lim ◽  
Zhen Ding ◽  
Hendra Purnawali
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Crack Closure ◽  
Working Condition ◽  
Position Control ◽  
Niti Shape Memory Alloy ◽  
High Recovery ◽  
Niti Sma ◽  
Recovery Strain ◽  
Shape Restoration

Because of the high actuation stress and high recovery strain, NiTi shape-memory alloy (SMA) has been proposed for shape/position control and crack closure in structures for many years. In this paper, we demonstrate the feasibility to use NiTi SMA for not only crack closure, but also shape restoration in a silicon/nanoclay composite beam. Instead of embedding SMA into the beam, we use a piece of external SMA wire so that the expensive NiTi SMA can be reused. In addition, both shape restoration and crack closure can be achieved even when the beam is still in working condition, i.e., with external load applied.

scholarly journals First-Principles Calculations of Structural, Mechanical, and Electronic Properties of the B2-Phase NiTi Shape-Memory Alloy Under High Pressure

Computation ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 57 ◽  
Author(s):  
Fang Yu ◽  
Yu Liu
Keyword(s):  
High Pressure ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Electronic Properties ◽  
First Principles ◽  
First Principles Calculation ◽  
Niti Shape Memory Alloy ◽  
Volume Deformation ◽  
Niti Sma ◽  
B2 Phase

A first-principles calculation program is used for investigating the structural, mechanical, and electronic properties of the cubic NiTi shape-memory alloy (SMA) with the B2 phase under high pressure. Physical parameters including dimensionless ratio, elastic constants, Young’s modulus, bulk modulus, shear modulus, ductile-brittle transition, elastic anisotropy, and Poisson’s ratio are computed under different pressures. Results indicate that high pressure enhances the ability to resist volume deformation along with the ductility and metallic bonds, but the biggest resistances to elastic and shear deformation occur at P = 35   GPa for the B2-phase NiTi SMA. Meanwhile, the strong anisotropy produced by the high pressure will motivate the cross-slip process of screw dislocations, thereby improving the plasticity of the B2-phase NiTi SMA. Additionally, the results of the density of states (DOS) reveal that the B2-phase NiTi SMA is essentially characterized by the metallicity, and it is hard to induce the structural phase transition for the B2-phase NiTi SMA under high pressure, which provides valuable guidance for designing and applying the NiTi SMA under high pressure.

Corrosion Resistance of NiTi Shape Memory Alloy after Nitriding and Oxynitriding Processes under Glow Discharge Conditions for Medical Applications

2016 ◽  
Vol 687 ◽  
pp. 92-97 ◽  
Author(s):  
Janusz Kamiński ◽  
Justyna Witkowska ◽  
Tadeusz Wierzchoń
Keyword(s):  
Corrosion Resistance ◽  
Glow Discharge ◽  
Shape Memory ◽  
Surface Topography ◽  
Niti Alloy ◽  
Nitrided Layer ◽  
Nickel Content ◽  
Corrosion Current ◽  
Niti Shape Memory Alloy ◽  
Initial State

NiTi alloy is being increasingly used in medicine due to its unique properties, i.e. shape memory and superelasticity. As a self-passivating material it is characterized by relatively high biocompatibility, however its use for long-term medical implants is questionable due to the nickel content of ≥ 50%. Therefore, the investigations on the surface modification of NiTi alloy are carried out to improve its corrosion resistance and thus reduce the metalosis effect, i.e. the migration of the alloy constituents, especially nickel, into the surrounding tissue.In this paper, the surface topography and corrosion resistance of NiTi alloy (50,8%Ni) both before and after low-temperature nitriding and oxynitriding processes under glow discharge conditions, are presented.The study of surface topography showed a slight increase in roughness parameters after nitriding process and a significant increase in these parameters after the oxynitriding process. A similar trend was observed in the study of corrosion resistance. Both processes increase the corrosion resistance of NiTi alloy, as shown by both the impedance spectroscopy results, the values of corrosion potential (-65 mV for the alloy in the initial state, - 45 mV for the alloy with the nitrided layer, + 18 mV for the alloy with the oxynitrided layer) and the values corrosion current (respectively 0.047 μA/cm2, 0.043 μA/cm2, 0.015 μA/cm2).These comparative studies present an improvement of corrosion resistance of NiTi after the processes under glow discharge. The best results were obtained for the oxynitrided layer.

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