Orientation relationships in precipitation systems
Based on a survey of the literature on orientation relationships in precipitation systems a unified view of all the known relationships in b.c.c./h.c.p. and b.c.c./f.c.c. systems is presented. Within each set of crystal systems, orientation relationships are closely connected by small fixed rotations whose magnitude depends only on crystal symmetries. Close parallels exist between the two sets of crystal systems, b.c.c./f.c.c. and b.c.c./h.c.p. The regularities observed in the literature survey lead to the hypothesis that precipitate and matrix tend to be related by an invarient line strain. The relative rotation of the two lattices predicted by this hypothesis is determined as a function of the lattice parameter ratio and is consistent with a large number of experimental studies. In the analysis of simple non-coherent precipitate morphologies the criterion of directional mismatch is demonstrated to be superior to the often used planar mismatch criterion. The precipitate morphology sensitiviely reflects variations in orientation relationships. Morpholoeis of coherent and equilibrium semicoherent precipitates are governed by more complex criteria but are also dominated mainly by crystallographic requirements.
- Research Organization:
- Lawrence Berkeley Lab., CA
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6789508
- Journal Information:
- Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 30; ISSN AMETA
- Country of Publication:
- United States
- Language:
- English
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