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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)
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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MDPI and ACS Style

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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