Recovery Stress Associated with R-Phase Transformation in TiNi Shape Memory Alloy : Properties under Constant Residual Strain

Tobushi, Hisaaki; Kimura, Kimio; Sawada, Takayuki; Hattori, Takeharu; Peng, Lin

doi:10.1299/jsmea1993.37.2_138

Cited by 13 publications

(10 citation statements)

References 11 publications

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“…29,30 The R-phase reorientation (or detwinning) takes place in stage (ii) by growth of favourably orientated variants. 23 The critical stress for inducing the R-phase reorientation is very low 13,16,50 and almost insensitive to the change of testing temperatures, 16 while the critical stress for inducing B199 martensite reorientation gradually increases with decreasing testing temperatures. 48,51 Miyazaki and Otsuka found that the reorientation of the R-phase, which is induced by the appearance of dislocation networks, needs much higher stress than that of the R-phase induced by the appearance of precipitates, due to the fact that the dislocation networks can impede the twin boundary movement more strongly than the precipitates.…”

Section: Deformation Behaviour Of R-phasementioning

confidence: 99%

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R-phase transformation in NiTi alloys

Wang

Verlinden

Humbeeck

2014

Materials Science and Technology

110

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In near equiatomic NiTi alloys, the thermoelastic transformation between austenite and the R-phase shows unique properties, which make the R-phase transformation very promising for applications. In the present paper, the fundamental issues related to the R-phase transformation, especially the effects of different thermomechanical treatments, are reviewed. Inspired by the literature review, recent work on controlling the R-phase transformation temperature by low temperature aging treatments is summarised.

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Section: Deformation Behaviour Of R-phasementioning

confidence: 99%

“…It is reported that the maximum recovery stress can reach a value up to 374 MPa, depending on the heat treatment and residual strain in stage (v). 29,50,53 The stress-strain response of pseudoelastic behaviour associated with the R-phase transformation is illustrated in Fig. 3b.…”

Section: Deformation Behaviour Of R-phasementioning

confidence: 99%

R-phase transformation in NiTi alloys

Wang

Verlinden

Humbeeck

2014

Materials Science and Technology

110

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“…The progress of the transformation is governed by the transformation kinetics. The starting and completing conditions of MT [16][17] and of RPT [18] [19] are expressed by the linear bctions of stress and temperature, respectively. These functions represent the boundaries between two phases in the stress-temperature phase diagram, which are called the transformation lines.…”

Section: Transformation Line 331 Stress-temperature Phase Diagrammentioning

confidence: 99%

Thermomechanical Properties of TiNi Shape Memory Alloy

Tobushi

Ikai²,

Yamada

et al. 1996

J. Phys. IV France

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The thermomechanical properties of shape memory effect and superelasticity due to the martensitic transformation and the R-phase transformation of TiNi shape memory alloy were investigated experimentally. The transformation line, recovery stress and fatigue property due to both transformations were discussed for cyclic deformation. The thermomechanical properties due to the R-phase transformation were excellent for deformation with high cycles.

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“…Taking advantage of the B2 → R transformation due to the properties and behaviour of nitinol alloys [218] requires precise control of its course [249], especially its temperature range [225,[280][281][282], annealing temperature [283], and temperature [284] and ageing time [285]. The main positive effects of this transformation include not only increased fatigue strength [225,[280][281][282], but also considerable stability under cyclic changes in temperature and loads [225,281,286], quick response to temperature changes [250,276,281,284,287], and a narrow hysteresis loop [250,288]. Activation of the B2 → R transformation is favoured by annealing after plastic deformation [289,290], ageing of alloys with a relatively small advantage of nickel atomic concentration [239,240,249,261,273,[291][292][293], as well as cyclic temperature [283,285,294,295] and stresses changes [296,297].…”

Section: Methods and Tools Of Root Canal Preparation In Endodontic Treatmentmentioning

confidence: 99%

Is Gutta-Percha Still the “Gold Standard” among Filling Materials in Endodontic Treatment?

Dobrzańska¹,

Dobrzański²,

Dobrzański³

et al. 2021

Processes

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The paper is an extensive monographic review of the literature, and also uses the results of the authors’ own experimental research illustrating the noticed developmental tendencies of the filling material based on gutta-percha. The whole body of literature proves the correctness of the research thesis that this material is the best currently that can be used in endodontics. Caries is one of the most common global infectious diseases. Since the dawn of humankind, the consequence of the disease has been the loss of dentition over time through dental extractions. Both tooth caries and tooth loss cause numerous complications and systemic diseases, which have a serious impact on insurance systems and on the well-being, quality, and length of human life. Endodontic treatment, which has been developing since 1836, is an alternative to tooth extraction. Based on an extensive literature review, the methodology of qualifying patients for endodontic treatment was analyzed. The importance of selecting filling material and techniques for the development and obturation of the root canal during endodontic treatment was described. Particular attention was paid to the materials science aspects and the sequence of phase transformations and precipitation processes, as well as the need to ensure the stoichiometric chemical composition of Ni–Ti alloys, and the vacuum metallurgical processes and material processing technologies for the effects of shape memory and superelasticity, which determine the suitability of tools made of this alloy for endodontic purposes. The phenomena accompanying the sterilization of such tools, limiting the relatively small number of times of their use, play an important role. The methods of root canal preparation and obturation methods through cold side condensation and thermoplastic methods, including the most modern of them, the thermo-hydraulic condensation (THC) technique, were analyzed. An important element of the research hypothesis was to prove the assumption that to optimize the technology of development and obturation of root canals, tests of filling effectiveness are identified by the density and size of the gaps between the root canal wall, and the filling methods used and devices appropriate for material research, using mainly microscopy such as light stereoscopic (LSM) and scanning electron (SEM). The most beneficial preparations were obtained by making a longitudinal breakthrough of 48 natural human teeth, extracted for medical reasons, different from caries, with compliance with all ethical principles in this field. The teeth were prepared using various methods and filled with multiple obturation techniques, using a virtual selection of experimental variants. The breakthroughs were made in liquid nitrogen after a one-sided incision with a narrow gap created by a diamond disc using a materialographic cutter. The best effectiveness of the root canal filling was ensured by the technology of preparing the root canals with K3 rotary nitinol tools and filling the teeth with the THC thermoplastic method using the System B and Obtura III devices with studs and pellets of filling material based on gutta-percha after covering the root canal walls with a thin layer of AH Plus sealant. In this way, the research thesis was confirmed.

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Recovery Stress Associated with R-Phase Transformation in TiNi Shape Memory Alloy : Properties under Constant Residual Strain

Cited by 13 publications

References 11 publications

R-phase transformation in NiTi alloys

R-phase transformation in NiTi alloys

Thermomechanical Properties of TiNi Shape Memory Alloy

Is Gutta-Percha Still the “Gold Standard” among Filling Materials in Endodontic Treatment?

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