EXPERIMENTAL-DETERMINATION AND SYMMETRY RELATED ANALYSIS OF ORIENTATION RELATIONSHIPS IN HETEROPHASE INTERFACES - A CASE-STUDY IN THE ZR-B SYSTEM

Orientation relationships between phases in the Zr-B binary system wer e determined using electron diffraction. Heterophase interfaces were p roduced during the solidification of the eutectic (Zr-ZrB2) followed b y phase transformation, i.e. allotropic transformation of zirconium, f ormation of ZrB by peritectoid transformation and stabilisation of a m etastable Zr phase, chi Zr. Despite the complexity of the various phas es and their transformation upon cooling, the experimental analysis of all the orientation relationships (cubic-hexagonal and hexagonal-hexa gonal) found in this system yields only three sets of orientations cha racterised by the parallelism of low index planes and directions. Usin g symmetry considerations and group theory, it has been demonstrated t hat these orientations can be understood as the lowest energy configur ations which can be produced from one single orientation formed at hig h temperature between beta Zr and ZrB2. Copyright (C) 1996 Acta Metall urgica Inc.