The Crystal Structure and the Phase Transition of a Metastable Phase in the Au-37.8% Zn Alloy

概要

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The alloy of the composition of nearly Au : Zn=5 : 3 forms the β'-phase with the ordered β-brass type structure above 500℃. When this alloy is rapidly cooled from 600℃ to room temperature, a metastable phase is formed, and if it is annealed at 200℃ for more than an hour, it transforms into the stable phase, Au_5Zn_3. The crystal structure of the metastable phase has been determined by X-ray diffraction using single crystals. The unit cell is orthorhombic with the dimensions of a_m=6.332, b_m=8.953 and c_m=4.477 kX, and a probable space group is Pmc 2_1. The atomic arrangement is fundamentally of the body-centered cubic lattice type, but atoms are located in positions slightly shifted from the lattice points of the fundamental lattice. All of atoms have components of shifts along the c_m-axis which are considered to be due to a relative gliding of every two (011) atomic planes of the original β'-phase lattice along the [011] direction. There are six equivalent orientation relationships between the unit cell of the metastable phase and that of the original β'-phase. They are expressed as follows : (100)_m//{100}β' [010]_m//<011>β'.
東北大学の論文
1967-00-00