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A Study on the Nanoparticles Evolution in Isothermally Aged Strain Glass of Ti48.7Ni51.3 Shape Memory Alloy by In Situ Small-Angle X-ray Scattering

1
Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan
2
Nuclear Fuel and Materials Division, Institute of Nuclear Energy Research, Taoyuan 325, Taiwan
3
Department of Mechanical Engineering, National Taiwan University, Taipei 106, Taiwan
*
Author to whom correspondence should be addressed.
Metals 2018, 8(5), 352; https://doi.org/10.3390/met8050352
Received: 6 March 2018 / Revised: 20 April 2018 / Accepted: 11 May 2018 / Published: 14 May 2018
(This article belongs to the Special Issue In Situ X-Ray Diffraction on Metals and Alloys)
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Abstract

Ni-rich nanodomains and Ti3Ni4 nanoprecipitates in the strain glass of Ni-rich Ti-Ni shape memory alloys (SMAs) play an important role in the origin and characteristic control of the strain glass transition. Ni-rich nanodomains are formed in the quenching process and dissolve during isothermal aging. Ti3Ni4 nanoprecipitates nucleate, grow and coarsen during aging. This study performed in situ small-angle X-ray scattering (SAXS) and ex situ X-ray diffraction to investigate the structural evolutions with aging time of nanoparticles in Ti48.7Ni51.3 SMA aged isothermally at 250 °C in terms of relative volume fraction, radius, thickness, orientation, lattice ordering, and morphology. The mechanism and kinetics of the concurrent phase evolutions of Ni-rich nanodomains and Ti3Ni4 nanoprecipitates are revealed and discussed in detail. Frequency-dependent storage modulus vs. temperature at different frequencies for different aging times was measured to characterize the strain glass transition. Quantitative correlation of all structural evolutions and kinetics of Ni-rich and Ti3Ni4 nanoparticles with respect to the variation and loss of the strain glass transition during aging times of 0 to 20 h is presented. The roles of different nanoparticles in causing or suppressing the strain glass behavior are also experimentally revealed. View Full-Text
Keywords: Ni-rich TiNi shape memory alloys; strain glass transition; small angle X-ray scattering; aging Ni-rich TiNi shape memory alloys; strain glass transition; small angle X-ray scattering; aging
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Huang, Y.-C.; Tsao, C.-S.; Wu, S.-K. A Study on the Nanoparticles Evolution in Isothermally Aged Strain Glass of Ti48.7Ni51.3 Shape Memory Alloy by In Situ Small-Angle X-ray Scattering. Metals 2018, 8, 352.

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