日本金属学会誌

J. Japan Inst. Metals, Vol. 54, No. 12 (1990),
pp. 1302-1307

Structure of Lamellae in ζβ-FeSi2

Naoto Sumida1, Tsuneo Mishima2 and Hiroshi Fujita3

1Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Suita
2Graduate Student, Osaka University, Suita. Present address: Central Research Laboratory, Kyocera Co. Ltd., Kagoshima
3Department of Materials Science and Engineering, Faculty of Engineering, Osaka University, Suita. Present address: Research Institute for Science and Technology, Kinki University, Higashi-Osaka

Abstract:

A tetragonal high-temperature phase (ζα-phase) and an orthorhombic low-temperature phase (ζβ-phase) exist in iron disilicide FeSi2. Electron microscope observation shows that most of the grains in the ζβ-phase alloy have lamellae.
These lamellae produce streaks perpendicular to the (100) plane in a diffraction pattern of the [021] zone axis. Contrast of the lamellae in a bright field image observed from the exact [011] zone axis disappears completely. There is no irregularity on the periodic arrangement of bright dots in a lattice image taken from the [011] zone axis. Therefore, it is concluded from these results that the lamellae are not thin precipitates but stacking faults on the plane parallel to the (100) plane with the [011] displacement vector.
Comparing the observed lattice image taken from the [021] zone axis with the simulated image, the positions of bright dots are assigned to be a group of iron atom rows lying in the first and the sixth stacking plane along the [100] direction in the unit cell. Taking into the consideration of the crystal structure of the ζβ-phase, we suggest the stacking fault is formed by the 1/2 [011] displacement between the third and the fourth stacking plane in the unit cell.


(Received 1990/7/18)

Keywords:

β-iron disilicide, lamella, stacking fault, diffraction pattern with streaks, lattice image of lamella


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