Phase transformations in /sup 16/Nb to 40% zirconium alloys above the monotectoid temperature. I

Journal Article · Tue Jan 01 00:00:00 EST 1974 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(74)90125-4· OSTI ID:7087805

Flewitt, P E.J.

The precipitation processes which occur on ageing metastable beta phase specimens above the monotectoid temperature (T/sub mono/) are established. The precipitation has been studied by optical and electron microscopy together with electron and x-ray diffraction. Spinodal decomposition of metastable beta has been confirmed in the initial stages by direct observation of modulations and the presence of side bands to main reflections in electron and x-ray diffraction patterns. The upper temperature limit of this coherent spinoidal decomposition T/sub s/ varies with composition and agrees closely with that predicted by the model proposed by Cahn (1962). Initial compositional modulations form on (100) planes to give two coherent regions, one enriched and one depleted in zirconium. The morphology of the spinodal product is an interlocking network of (100) axis rods. The wavelength increases with ageing time and at T/sup 1/3/ obeys coarsening law. As the wavelength increases eventually coherency is lost between the two phases and (100) interfacial planes develop. The dislocation networks at these semicoherent interfaces comprise two sets of a (100) dislocations in edge orientation and one set of a (110) dislocations. 41 refs.

• Research Organization: CEGB, London
• OSTI ID: 7087805
• Journal Information: Acta Metall.; (United States), Vol. 22:1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
NIOBIUM BASE ALLOYS
PHASE TRANSFORMATIONS
PRECIPITATION HARDENING
ZIRCONIUM ALLOYS
DISLOCATIONS
ELECTRON DIFFRACTION
X-RAY DIFFRACTION
ALLOYS
COHERENT SCATTERING
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFRACTION
HARDENING
LINE DEFECTS
NIOBIUM ALLOYS
SCATTERING
360102* - Metals & Alloys- Structure & Phase Studies