Local structure and medium-range order in a glassy Ti-Ta-based surface alloy after low-temperature annealing studied by electron nano-beam diffraction

• Published in: Materials characterization 2021-04, Vol.174, p.110967, Article 110967
• Main Authors: Semin, V.O., Gudimova, E.Yu, Neiman, A.A., D'yachenko, F.A., Meisner, L.L.
• Format: Article
• Language: English
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2021.110967

The rejuvenated metallic glasses subjected to heat treatments show the improved thermal stability and properties. The atomic structure in the glassy alloys inherited from the liquid state possesses the medium-range order that could be significantly modified upon heating. In this work, we utilized the nano-beam diffraction technique to resolve the medium-range order in a glassy Ti-Ta-based surface alloy upon isothermal annealing. After annealing at T = 773 K the as-received Ti-Ni-Ta surface alloy, fabricated by a liquid-phase mixing of the system [Ti-Ta film/TiNi substrate], devitrified through the formation of a nanocrystalline structure: η′-(Ti,Ta)2Ni + β(Ti,Ta) + α″(Ti,Ta). The transmission electron microscopy methods were employed to determine the parameters of the short-range order in the amorphous phase both in the reciprocal and real spaces. For interpretation of the results of the electron scattering in the reciprocal space, the coherent and diffuse scattering intensities were calculated in the framework of the multi-shell cluster model. We suggested a scheme describing the transformations of icosahedral nanoclusters during the temperature-induced rejuvenation. A methodology on the selection of the validated two-shell cluster model reproducing the medium-range order was proposed. [Display omitted] •The thermal stability of a glassy Ti-Ta-based surface alloy was studied.•During the relaxation annealing, the medium-range order structure was modified.•The atomic structure studied by the electron nano-beam diffraction could be described by the two-shell icosahedral clusters.•A scheme of the evolution of the cluster structure in the glassy surface alloy was proposed.