Acta Crystallographica Section A

Foundations of Crystallography

Volume 59, Part 2 (March 2003)

research papers

Acta Cryst. (2003). A59, 153-162 [ doi:10.1107/S0108767302022316 ]

Theory of diffraction from D0₁₉ ordered c.p.h. structures containing complex stacking faults on basal planes

P. Ghosal and S. Lele

Abstract: Antiphase boundaries and stacking faults affect the deformation behaviour of intermetallics. In an ordered c.p.h. (close-packed hexagonal) structure of D0₁₉ type (e.g. Mg₃Cd, Ti₃Al-based alloys), stable planar faults of two types are possible on the basal plane. These are antiphase boundaries (APBs) and complex stacking faults (CSFs), which are a combination of an APB and a stacking fault. The latter can be either of shear or of climb type. If the bounding partial dislocations of a CSF lie in its plane, then it is designated as a shear CSF, otherwise it is called a climb CSF. A mathematical formulation of the theory of diffraction from a D0₁₉ structure having a shear or climb type of CSF has been carried out. The diffraction effects owing to the presence of these CSFs have been found. Integrated intensities and widths of the reflections are affected. These have been evaluated in terms of the probability of the occurrence of these faults.

Keywords: close-packed hexagonal structures; stacking faults; D0₁₉ ordered structures.