Morphological aspects of. cap alpha. ''-Fe/sub 16/N/sub 2/ precipitation in. cap alpha. -Fe
The intermediate precipitate ..cap alpha..''-Fe/sub 16/N/sub 2/ formed during the quench-aging of nitrogen-ferrite occurs via a nitrogen GP zone stage as thin disc-shaped plates on the three sets of matrix (001) planes. Its b.c. tetragonal structure can be considered as a tetragonal distortion of ferrite with an expansion (9.7%) in the c/sub -/-direction and a slight contraction (0.2%) in the a/sub -/-direction due to the ordered occupation by nitrogen atoms of two of the sixteen octahedral interstices whose tetrad axes are parallel with one of the cube directions, i.e. the c/sub -/-edge. Previous TEM studies on ..cap alpha..'' precipitation have been performed using bulk-aging and in-situ aging procedures and, irrespective of which aging treatment is adopted, individual disc-shaped ..cap alpha..'' particles always have a characteristic ''rosette'' contrast when viewed normal to the plate surface. This effect has not been explained but was thought to originate through variations of the plate thickness or anisotropy of surface energy. The present TEM analysis using high-angle tilting shows that this contrast arises because individual ..cap alpha..'' particles are comprised of several inclined segments near the same (001) plane.
- Research Organization:
- Materials and Molecular Research Division, Lawrence Berkeley Laboratory, Berkeley, CA
- OSTI ID:
- 6463887
- Journal Information:
- Scr. Metall.; (United States), Vol. 18:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IRON-ALPHA
MICROSTRUCTURE
CHEMICAL REACTION YIELD
ELASTICITY
FERRITES
IRON COMPOUNDS
IRON NITRIDES
MATHEMATICAL MODELS
MORPHOLOGY
NITROGEN COMPOUNDS
PLATES
PRECIPITATION
QUENCH AGING
SURFACE AREA
TRANSMISSION ELECTRON MICROSCOPY
AGING
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
ELEMENTS
FERRIMAGNETIC MATERIALS
IRON
MAGNETIC MATERIALS
MATERIALS
MECHANICAL PROPERTIES
METALS
MICROSCOPY
NITRIDES
OXYGEN COMPOUNDS
PNICTIDES
SEPARATION PROCESSES
SURFACE PROPERTIES
TENSILE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
YIELDS
360102* - Metals & Alloys- Structure & Phase Studies