Atomic structure of nanoscale quasicrystal-forming Zr–noble metal binary metallic glasses

• Published in: Journal of alloys and compounds 2011-06, Vol.509, p.S27-S33
• Main Authors: Saida, J., Itoh, K., Sanada, T., Sato, S., Imafuku, M., Ohnuma, M., Inoue, A.
• Format: Article
• Language: English
• Subjects: Alloys; Local structure; Metallic glasses; Nanostructure; Palladium; Polyhedrons; Quality control; Quasicrystallization; Simulation; Zirconium; Zirconium base alloys; Zirconium-based alloy
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2010.12.076

▶ Zr 70Pd 30 and Zr 80Pt 20 are the quasicrystal (QC)-forming glassy alloys. ▶ The QC phase precipitates by a cooperative motion of atoms or clusters. ▶ Relatively perfect icosahedrons frequently exist around Zr in Zr 70Pd 30, however, distorted icosahedral-like clusters are formed around Zr and Pt in Zr 80Pt 20. ▶ The QC phase formation originates from a different mechanism in the two alloys. We report the results of the local structural evaluation and mechanism of QC formation in the Zr 70Pd 30 and Zr 80Pt 20 glassy alloys. Voronoi analysis indicates the difference of local environment between two alloys. The perfect icosahedron frequently exists around Zr atom and major polyhedra have prism-like structure around Pd in Zr 70Pd 30. In contrast, icosahedral-like distorted polyhedra formation is favorable around Pt as well as Zr in Zr 80Pt 20. It is therefore, concluded that the quasicrystallization originates from the medium-range order based on the Zr-centered perfect icosahedron and the Pd-centered prism-like ones remain during the QC phase formation in Zr 70Pd 30. Icosahedral-like local structure around Zr and Pt might contribute together to the nucleation of QC phase in Zr 80Pt 20. This feature with a different mechanism of QC formation in the two alloys may correlate to the difference of solute concentration and the structure of stable crystalline phase after the decomposition of QC phase.