Thermal recovery processes in deformed aluminum
The effects of recovery on both microstructure and subsequent stress vs strain behavior were studied in pure aluminum single crystals prestrained at room temperature at <111> compression; they are presumed to be representative of polycrystal behavior, avoiding changes in grain structure. Transmission electron microscopy showed that two distinct dislocation processes occur: (1) a rapid tightening of tangles and loose cell walls, eventually into subgrain boundaries, without a noticeable change in the scale of the structure, and (2) subsequent coarsening of the subgrain structure. These two processes of microstructural change were correlated respectively with two distinct types (I and II) of stress vs strain behavior during postanneal straining. After Type I recovery, the relation between the strain-hardening rate, theta = d sigma/d epsilon (sigma: true stress, epsilon: true strain), and the true stress is identical to that of an unrecovered specimen, after a transient of a few percent of post-anneal straining. Type I recovery encompasses all of metarecovery and part of orthorecovery, and bears resemblance to dynamic recovery processes during stage III strain-hardening. Type II recovery, which succeeds Type I recovery, shows long-lasting effects on the mechanical behavior which are characterized in particular by unusually low theta values compared to unrecovered specimens deformed to the same stress. It may correspond to some transition stage between recovery and recrystallization. 7 figures.
- Research Organization:
- Argonne National Lab., IL
- OSTI ID:
- 5458347
- Journal Information:
- Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 27; ISSN AMETA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360103* -- Metals & Alloys-- Mechanical Properties
360104 -- Metals & Alloys-- Physical Properties
ALUMINIUM
ANNEALING
COMPRESSION
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DISLOCATIONS
ELECTRON MICROSCOPY
ELEMENTS
GRAIN BOUNDARIES
HARDENING
HEAT TREATMENTS
HIGH TEMPERATURE
LINE DEFECTS
MECHANICAL PROPERTIES
METALS
MICROSCOPY
MICROSTRUCTURE
MONOCRYSTALS
PRESSURE DEPENDENCE
RECRYSTALLIZATION
STRAIN HARDENING
STRAIN RATE
STRAINS
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
TIME DEPENDENCE