Crystallography and a model of the α → ω phase transformation in zirconium

A. Rabinkin, M. Talianker, O. Botstein

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The omega phase in pure Zr formed at 300 K under high pressure of 6.0 G Pa was examined using high resolution dark-field electron microscopy and selected area diffraction. Pressurized Zr has a two phase structure consisting of small elongated ellipsoidal ω particles of d ∼- 40-50 A ̊ and l = 100-120 A ̊ which are precipitated in an α matrix. There is a strong resemblance between morphologies of omega originated in either α or β. The principally new orientation relationship between α and ω phase is established. There are three possible orientations (variants) of ω in an α matrix. The basal (0001) plane of α is parallel to {12̄10} and the [0001] direction coincides with everyone of the three directions of α: [ 2 ̄1101, [ 1 ̄ 1 ̄20]2) and [ 1 ̄2 1 ̄0]3) with deviations ~ ±5-7°. The atomistic model explaining the data obtained is proposed. The α → ω transformation is regarded as a displacive type. According to the model, every three neighbouring close-packed atomic rows [12̄10]x are displaced in a basal plane (0001)x on a distance ax 4 along [12̄10]x direction and the next three along the opposite direction [1̄21̄0]x and so on. Such displacements accompanied by small shuffles form {12̄10} planes. The common traits in α → ω and β → ω transformations are also discussed together with possible mechanism of the appearance of linear defects along closepacked rows necessary for displacive transformations in Zr (Ti) and its alloys.

Original languageEnglish
Pages (from-to)691-698
Number of pages8
JournalActa Metallurgica
Issue number4
StatePublished - 1 Jan 1981

ASJC Scopus subject areas

  • Engineering (all)


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