Fundamental Development on Utilizing the R-phase Transformation in NiTi Shape Memory Alloys

Wang, Xiebin; Kustov, S.; Verlinden, Bert; Humbeeck, Jan Van

doi:10.1007/s40830-015-0007-2

Cited by 50 publications

(22 citation statements)

References 43 publications

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“…precipitation to occur only a few seconds in the 500 to 300 ⁰C temperature range are required [55]. The existence of R-phase is then favoured by presence of these precipitates as comprehensively described in [56,57]. Finally, the presence of Ni4Ti3 in the as-built parts promotes a Ni depletion from the matrix, thus justifying the increased transformation temperatures of the WAAM deposited material as described above, as increase in hardness along the wall height.…”

Section: Phase Transformation Characteristicsmentioning

confidence: 94%

Wire and arc additive manufacturing of a Ni-rich NiTi shape memory alloy: Microstructure and mechanical properties

Zeng

Cong

Oliveira

et al. 2020

Additive Manufacturing

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Wire and Arc Additive Manufacturing (WAAM) was used for fabrication of NiTi parts using a commercialy available Ni-rich NiTi wire as the feedstock material. The as-built parts are near fully austenitic at room temperature as confirmed by differential scanning calorimetry, X-ray diffraction and superelastic cycling. The as-built microstructure changed from collumnar, in the first deposited layers, to equiaxed in the last deposited ones as a result of the different thermal cycle conditions. This is the 2 first work where WAAM NiTi parts exhibit superelastic behavior under tensile conditions, highlighting the potential use of the technique for the creation of parts shaped in a complex manner based on this material and process. The potential to use WAAM for deposition of advanced functional materials is demonstrated.

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Section: Phase Transformation Characteristicsmentioning

confidence: 94%

Wire and arc additive manufacturing of a Ni-rich NiTi shape memory alloy: Microstructure and mechanical properties

Zeng

Cong

Oliveira

et al. 2020

Additive Manufacturing

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“…The precipitation of Ni-rich Ni 4 Ti 3 particles is also a possible reason for the increase of MTTs [ 42 ], because the formation of Ni 4 Ti 3 particles leads to Ni-depletion from the matrix [ 1 , 2 ]. However, the Ni 4 Ti 3 precipitates are normally very small in SLM fabricated NiTi alloys [ 42 , 56 ], and nano-sized Ni 4 Ti 3 precipitates indeed suppress martensite transformation (MT), instead of promoting MT, due to the intense lattice distortion that is caused by the coherency between Ni 4 Ti 3 and B2 matrix [ 90 , 91 , 92 ].…”

Section: Phase Transformation Behaviormentioning

confidence: 99%

A Short Review on the Microstructure, Transformation Behavior and Functional Properties of NiTi Shape Memory Alloys Fabricated by Selective Laser Melting

2018

Self Cite

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Due to unique functional and mechanical properties, NiTi shape memory alloys are one of the most promising metallic functional materials. However, the poor workability limits the extensive utilization of NiTi alloys as components of complex shapes. The emerging additive manufacturing techniques provide high degrees of freedom to fabricate complex structures. A freeform fabrication of complex structures by additive manufacturing combined with the unique functional properties (e.g., shape memory effect and superelasticity) provide great potential for material and structure design, and thus should lead to numerous applications. In this review, the unique microstructure that is generated by selective laser melting (SLM) is discussed first. Afterwards, the previously reported transformation behavior and mechanical properties of NiTi alloys produced under various SLM conditions are summarized.

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“…Additive technologies [232], drawing [233] or cold rolling [234], high-pressure torsion (HPT) [235], and equal channel angular pressing (ECAP) [236] can also be used for the manufacturing of tools using nitinol alloy. The favourable fineness of the austenitic matrix grain [237,238] depends on the heat treatment conditions [239,240] and the given technological processes, deciding the course of the Ni 4 Ti 3 [241,242] dispersion precipitation processes in austenite and martensitic transformation, respectively, in the B19 or R structure phases [242,243].…”

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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Fundamental Development on Utilizing the R-phase Transformation in NiTi Shape Memory Alloys

Cited by 50 publications

References 43 publications

Wire and arc additive manufacturing of a Ni-rich NiTi shape memory alloy: Microstructure and mechanical properties

Wire and arc additive manufacturing of a Ni-rich NiTi shape memory alloy: Microstructure and mechanical properties

A Short Review on the Microstructure, Transformation Behavior and Functional Properties of NiTi Shape Memory Alloys Fabricated by Selective Laser Melting

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

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