Precipitation of. gamma. -zirconium hydride in zirconium

Journal Article · Tue Aug 01 04:00:00 EDT 1978 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(78)90006-8· OSTI ID:6487245

Carpenter, G J.C.

A mechanism for the precipitation of ..gamma..-zirconium hydride in zirconium is presented which does not require the diffusion of zirconium. The transformation is completed by shears caused by 1/3 (10 anti 10) Shockley partial dislocations on alternate zirconium basal planes, either by homogeneous nucleation or at lattice imperfections. Homogeneous nucleation is considered least likely in view of the large nucleation barrier involved. Hydrides may form at dislocations by the generation of partials by means of either a pole or ratchet mechanism. The former requires dislocations with a component of Burgers vector along the c-axis, but contrast experiments show that these are not normally observed in annealed zirconium. It is therefore most likely that intragranular hydrides form at the regular 1/3 (11 anti 20) dislocations, possibly by means of a ratchet mechanism. Contrast experiments in the electron microscope show that the precipitates have a shear character consistent with the mechanism suggested. The possibility that the shear dislocations associated with the hydrides are emissary dislocations is considered and a model suggested in which this function is satisfied together with the partial relief of misfit stresses. The large shear strains associated with the precipitation mechanism may play an important role in the preferential orientation of hydrides under stress.

• Research Organization: Chalk River Nuclear Lab., Ont.
• OSTI ID: 6487245
• Journal Information: Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 26:8; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210000 -- Nuclear Power Plants
36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOYS
CRYOGENIC FLUIDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DIFFUSION
DISLOCATIONS
ELECTRON MICROSCOPY
ELEMENTS
FLUIDS
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
LINE DEFECTS
METALS
MICROSCOPY
NONMETALS
PHASE TRANSFORMATIONS
PRECIPITATION
REACTOR MATERIALS
SEPARATION PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TRANSMISSION ELECTRON MICROSCOPY
ZIRCONIUM
ZIRCONIUM ALLOYS
ZIRCONIUM COMPOUNDS
ZIRCONIUM HYDRIDES