Theoretical Properties of Ni2Ti alloys Studied :by Gaussian 09 Program

Due to the combination of excellent mechanical properties, high chemical stability and appropriate biocompatibility, the Ni-based alloys find large application in implantology and dentistry. The traditional metallurgical synthesis methods of these alloys have some difficulties leading to inconstancy of the composition, degradation of properties and escalation of the product price. Here we show how to overcome the disadvantages of the traditional methods of synthesis and production of Ni-based alloys for medical application using combination of mechanochemical and powder-metallurgical routes. The structural properties of the products were studied using SEM/TEM and XRD methods. It was shown that the mechanically assisted synthesis allows obtaining nanosized Ni-Ti alloy with mean particle size of 20-30 nm at significantly lower temperature in comparison with the traditional metallurgical high-temperature alloying. It was also shown that after 40 hours of intense mechanical treatment of the starting Ni and Ti powders, a direct synthesis of Ni-Ti alloy proceeds. The product has excellent sinterability which allows producing bodies with controlled structural properties appropriate for application in implantology. Using standard mechanical tests and structural examinations it was demonstrated that the Ni-Cr dental alloys obtained by mechanically assisted sintering and casting possess excellent mechanical, technological and aesthetic properties. These alloys are suitable as dental restoration materials and production of porcelain veneered constructions like crowns and bridges using the so called metal-to-ceramic technique.

It is well established that Ni/Ti is categorize as a shape memory alloy. They found great interesting application including aerospace, biomedical and so many others. However, there is possibility of corrosion of these alloys in physiological solution and dissolution of toxic Ni-ions. Laser surface treatment technique was adopted in this work. An improvement inNi-ion dissolution reduction of (310%) was obtained in Nd-YAG laser surface-treated samples. Great enhancement in corrosion resistance of (1549%) also occurred. A substantial improvement in hardness of (368%) was recorded in laser treated samples.

Materials Letters, 2009

Disordered B2-NiTi intermetallic phase was produced from a mixture of Ni and Ti powders by mechanical alloying (MA). X-ray technique was used for phase analysis. The results indicated that Ni(Ti) solid solution can be formed earlier and changed to disordered B2-NiTi intermetallic phase after 60 h of MA. A thermodynamic analysis of the process was then carried out using Miedema model. The results showed that there is a thermodynamic driving force in Ni-Ti binary to form solid solution at all compositions and amorphous phase in the composition range X Ni : 0.05-0.95 where X Ni is mole fraction of Ni. However, the stable phase which has the minimal Gibbs free energy is solid solution compared to amorphous phase at all compositions. The results of MA were compared with thermodynamic analysis and it was indicated that the product of MA is the most stable phase in Ni-Ti binary system.

Le Journal de Physique IV, 1997

The behaviour of Ni-Ti and Copper Ni-Ti orthodontic wircs was tcsted undcr induccd torsion in controlled conditions of moment and temperature. The results clearly demonstrate a great diffcrcncc in the behaviour of thcsc wires. The loading and unloading curves and plateau rcgions were found to bc closcly mlatcd to tcmpcraturc. Experiments carried out in conditions of identical toision revealed significant variations in stiffness duc to changcs in mouth temperature. Divcrsity of reaction to stress is linked to the crystalline struclurc of the alloys.-' the tested wires is 0.017 x 0.025 inches (0.435 x 0.64 1iim2) or 0.01 S s 0.025 inches (0.36 x 0.64 mm2).

Molecules, 2022

Nickel–titanium alloys used in dentistry have a variety of mechanical, chemical, and biofunctional properties that are dependent on the manufacturing process. The aim of this study was to compare the mechanical and biofunctional performances of a nickel–titanium alloy produced by the continuous casting method (NiTi-2) with commercial nitinol (NiTi-1) manufactured by the classical process, i.e., from remelting in a vacuum furnace with electro-resistive heating and final casting into ingots. The chemical composition of the tested samples was analyzed using an energy dispersive X-ray analysis (EDX) and X-ray fluorescence (XRF). Electron backscatter diffraction (EBSD) quantitative microstructural analysis was performed to determine phase distribution in the samples. As part of the mechanical properties, the hardness on the surface of samples was measured with the static Vickers method. The release of metal ions (Ni, Ti) in artificial saliva (pH 6.5) and lactic acid (pH 2.3) was measured...

Materials Today: Proceedings, 2019

In recent decades, researches and analysis for applying the Ni-Ti alloys have become increasingly more specific, tending to studies on micro and nano actuators targeting applications in medical and orthodontic devices and in electromechanical microsystems. Thus, the welding processes have become important allies by promoting the union between shape memory alloy actuators (SMA) with similar and dissimilar ones, which is one way of increasing the useful applications of available materials, especially biomaterials. In this context, this study aimed atanalyzing the corrosion resistance in the weld region obtained by autogenous TIG micro welding in Ni-Ti superelastic wires with thermo-active Ni-Ti wires in a solution that simulates human saliva. The welded wires heat treatment made based on a factorial design 3 2. The results revealed that the TIG welding process used in this work generated welds of excellent quality, showing a good resistance to corrosion in the electrolyte that simulates human saliva. The experimental design used to investigate the influence of temperature and time of heat treatment in corrosion results generated a great experiment with temperature of 350 °C and time in the range of 20 minutes. This result was confirmed by means of electrochemical impedance spectroscopy tests.

Dental Materials Journal, 2001

2019

The orthodontic files have been used in dentistry since the middle ages and, as so, the shape, material and operation mode have changed since those days. In the late days, we have seen an increasing use of Nickel-Titanium (NiTi) alloys, to the detriment of more conventional alloys. At body temperature, these NiTi alloys present a superelastic behaviour, which allow the file to follow the teeth root in an easier way comparing to conventional alloys and have been reported to be more effective in the removal of the tooth pulp tissue, and in the protection of the tooth structure. Notwithstanding, these NiTi instruments, as all the others being subjected to bending loading, they fracture without any visual signal of degradation. Thereby, there is a need of studying these alloys, as they present a high hysteresis cycle and a high non-linearity in the Elastic Domain. Currently, there is not an international standard for these alloys, so various authors have attempted to design systems that...

Computational Materials Science, 2009

The effects of alloying elements (Co,

2014

The equiatomic alloy of nickel and titanium, known as nitinol, possesses unique properties such as superelasticity, pseudoplasticity, shape memory, while maintaining good corrosion resistance and sufficient biocompatibility. Therefore it is used for production of various devices including surgery implants. Heat treatment of nickel-rich NiTi alloys can result in precipitation of nickel-rich phases, which strongly influence tensile and fatigue behaviour of the material. In this work we have studied influence of short-period heat treatment on tensile behaviour and fatigue life of the NiTi (50.9 at. % Ni) wire intended for fabrication of surgery stents.

2013

This work is characterized by a comparative study of mechanical properties and corrosion resistance of alloys in common use and under consideration in orthodontics. The study is being conducted in three types of alloys, stainless steel 304V, Ni-Ti alloy which are the most common, and Ni-Free alloy Böhler latest, in order to compare their behavior with mechanical tension stress intraoral

Springer eBooks, 2017

Nickel-titanium (NiTi) orthodontic archwires are crucial in the initial stages of orthodontic therapy when the movement of teeth and deflection of the archwire are the largest. Their great mechanical properties come with their main disadvantage-the leakage of nickel. Various in vitro studies measured nickel leakage from archwires that were only immersed in the medium with little or minimal simulation of all stress and deflection forces that affect them. This study aims to overcome that by simulating deflection forces that those archwires are exposed to inside the mouth of a patient. NiTi orthodontic archwires were immersed in CACO2-2 cell culture medium and then immediately loaded while using a simulator of multiaxial stress for 24 h. After the experiment, the surface of the NiTi orthodontic archwires were analysed while using scanning electron microscopy (SEM) and auger electron spectroscopy (AES). The observations showed significant microstructural and compositional changes within the first 51 nm thickness of the archwire surface. Furthermore, the released nickel and titanium concentrations in the CACO2-2 cell culture medium were measured while using Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). It was found out that the level of released nickel ions was 1.310 µg/L, which can be assigned as statistically significant results. These data represent the first mention of the already detectable release of Ni ions after 24 h during the simulation of mechanical loading in the CACO2-2 cell culture medium, which is important for clinical orthodontic praxis.

Materials Chemistry and Physics, 2003

Investigations of the microstructure and mechanical properties of nitrided Ti–1Al–1Mn alloy were performed. The microstructural analyses were carried out using light microscopy, scanning electron microscopy and transmission electron microscopy (TEM). Phase identifications and chemical compositions of the bulk material and the layers were determined by electron diffraction as well as by energy-dispersive X-ray spectrometry. Scanning force microscopy (SFM) was applied for the alloy surface topography analysis. Microhardness and Young’s modulus measurements as well as scratch tests were performed. The investigations revealed a clear correlation between the nitriding process temperature, surface topography, microstructure, and mechanical properties of the alloy investigated.

Journal of Applied Research and Technology, 2017

The present paper describes the structural stability and mechanical properties of the ␥ phase for Ni-16Cr and Ni-16Mo alloys using first principles density functional theory (DFT) within generalized gradient approximation (GGA). The equilibrium lattice constant values of these alloys are in good agreement with the experimental data obtained by X-ray diffraction technique. The formation energy per atom values suggests that the ␥ phase of both alloys is stable. The Ni-16Mo alloy is energetically more stable than Ni-16Cr. Both alloys satisfy the Born stability criteria in terms of elastic constants and are associated with ductile behaviour based on shear to bulk modulus ratios. Both alloys show an anisotropic behaviour. The Ni-16Mo alloy exhibits higher anisotropy than the Ni-16Cr one.

Dental Press Journal of Orthodontics, 2012

Nickel-titanium alloys: A systematic review Objective: A systematic review on nickel-titanium wires was performed. The strategy was focused on Entrez-PubMed-OLDMEDLINE, Scopus and BioMed Central from 1963 to 2008. Methods: Papers in English and French describing the behavior of these wires and laboratorial methods to identify crystalline transformation were considered. A total of 29 papers were selected. Results: Nickel-titanium wires show exceptional features in terms of elasticity and shape memory effects. However, clinical applications request a deeper knowledge of these properties in order to allow the professional to use them in a rational manner. In addition, the necessary information regarding each alloy often does not correspond to the information given by the manufacturer. Many alloys called "superelastic" do not present this effect; they just behave as less stiff alloys, with a larger springback if compared to the stainless steel wires. Conclusions: Laboratory tests are the only means to observe the real behavior of these materials, including temperature transition range (TTR) and applied tensions. However, it is also possible to determine in which TTR these alloys change the crystalline structure.