Journal Article10.1002/PSSA.2210250240
Compositional changes associated with periodic antiphase boundaries in the initial stages of ordering in Ni3Mo1. I. Crystallographic Analysis
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TL;DR: In this article, a long period superlattice of 13.9 A is observed which can be attributed to a periodic array of non-conservative antiphase boundaries in the Ni3Mo-structure.
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Abstract: The early stages of ordering in Ni3Mo have been studied by electron diffraction and microscopy. A long period superlattice of 13.9 A is observed which can be attributed to a periodic array of non-conservative antiphase boundaries in the Ni3Mo-structure. This superlattice disappears by coarsening of the array after longer annealing times. From the shift of the superlattice reflections the displacement vector associated with the antiphase boundaries could unambigeously be determined as [102] using a method developed earlier for shear structures. This result is in agreement with the structural model and with the displacement vector as derived from image extinctions. Direct evidence is found for the shear transformation from the f.c.c. high temperature phase to the ordered Ni3Mo-structure, which is a superstructure of the h.c.p. structure.
Die fruhen Ordnungszustande in Ni3Mo wurden mit Elektronenmikroskopie und Elektronenbeugung untersucht. Es wird ein lang-periodisches Ubergitter von 13,9 A beobachtet, das einer periodischen Anordnung von nicht-konservativen Antiphasengrenzen in der Ni3Mo-Struktur zugeordnet werden kann. Dieses Ubergitter verschwindet durch Vergroberung der Anordnung nach langerer Temperungsdauer. Aus der Verschiebung der Ubergitter-Reflexionen last sich der Verschiebungsvektor, der mit den Antiphasengrenzen verknupft ist, eindeutig als [102] mit einer Methode bestimmen, die schon fruher fur Scherstrukturen entwickelt wurde. Dieses Ergebnis befindet sich in Ubereinstimmung mit dem Strukturmodell und mit dem aus der Bildextinktion bestimmten Verschiebungsvektor. Es wurde ein direkter Hinweis fur die Schertransformation von der k.f.z.-Hochtemperatur-phase zu der geordneten Ni3Mo-Struktur gefunden, die eine Uberstruktur der h.d.p.-Struktur ist.
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Citations
Non-commensurate (misfit) layer structures
E. Makovicky,B. G. Hyde +1 more
- 01 Jan 1981
TL;DR: In this article, the authors consider incommensurate structures of the type which have two more or less independent, though modulated, sub-lattices derived from misfitting layers of two types, alternating regularly in the layer-stacking direction.
121
The direct observation of discommensurations in barium sodium niobate (BSN) and its homologues
TL;DR: In this article, microscopic evidence for the presence of discommensuration walls in incommensurate ferro-electric-ferro-elastic Ba2NaNb5O15 and its homologues was presented.
66
The study of planar interfaces by means of electron microscopy
S. Amelinckx,J. Van Landuyt +1 more
- 01 Jan 1978
59
The DO22 Intermediate Phase in the Ni‐Mo System
TL;DR: In this article, a study of Ni3Mo by electron microscopy and electron diffraction reveals the presence of a new metastable intermediate phase during the early stages of ordering, known as the DO22 phase.
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References
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On the generation mechanism for shear planes in shear structures
J. Van Landuyt,S. Amelinckx +1 more
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Lattice relaxation at non-conservative antiphase boundaries in Ni3Mo†
G. Van Tendeloo,S. Amelincks +1 more
TL;DR: In this article, it is shown that if a small excess of molybdenum is present along the boundary, a relaxation of the lattice occurs along the interface, which gives rise to a small supplementary displacement vector ϵ, the total displacement vector being R ϵ.
29
A study of dissociated antiphase boundaries in Ni3Mo
TL;DR: In this article, a model for the splitting of antiphase boundaries has been proposed from structural considerations, and the predictions for the fault planes, the displacement vector and the Burgers vector of the attached dislocation are completely confirmed by the observations.
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