Recovery and facets for deformation twins in minerals and metals

Type II and IV twins with irrational twin boundaries are studied by high-resolution transmission electron microscopy in two plagioclase crystals. The twin boundaries in these and in NiTi are found to relax to form rational facets separated by disconnections. The topological model (TM), amending the...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2023-02, Vol.120 (8), p.e2215085120-e2215085120
Main Authors: Hirth, John P, Xie, Dongyue, Hirth, Greg, Wang, Jian
Format: Article
Language:English
Subjects:
Boundaries
Crystals
disconnections
dislocations
High resolution electron microscopy
MATERIALS SCIENCE
Metals
phase transformations
Physical Sciences
Plagioclase
Predictions
Transmission electron microscopy
Twin boundaries
twins
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Summary:Type II and IV twins with irrational twin boundaries are studied by high-resolution transmission electron microscopy in two plagioclase crystals. The twin boundaries in these and in NiTi are found to relax to form rational facets separated by disconnections. The topological model (TM), amending the classical model, is required for a precise theoretical prediction of the orientation of the Type II/IV twin plane. Theoretical predictions also are presented for types I, III, V, and VI twins. The relaxation process that forms a faceted structure entails a separate prediction from the TM. Hence, faceting provides a difficult test for the TM. Analysis of the faceting by the TM is in excellent agreement with the observations.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2215085120