Grain boundary phase equilibria in metallic systems: Progress report, December 1, 1987--November 30, 1988
A combined experimental and theoretical approach to treating the problem of grain boundary phase equilibrium is presented. On the theoretical side, volume dependent interionic potentials have been generated. A ..sigma.. = 5 bicrystal has been simulated with the constant pressure molecular dynamics method. The melting of the grain boundary before the bulk has been investigated. A liquid like layer replaces the solid interface at 1200 K. The disordering occurs above the bulk melting point. The slow kinetics of the process is thought to be the limiting factor for observing the phenomenon at lower temperatures. Analytical expressions for the elastic energy of a point defect near a general high angle grain boundary have been derived. These expressions predict two mechanisms for segregation: uniform segregation in the core of the grain boundary or formation of aggregates. On the experimental side, we have used strain annealing to grow large random bicrystals of 99.999% pure aluminum. Strain annealing and float zone refining are investigated as potential growth techniques for producing bicrystals with controlled misorientation. The procedure for preparing electron-transparent bicrystal specimens from the as grown large bicrystal is reported. We present the transmission electrons microscopy work preliminary to the high resolution microscopy on a symmetric near ..sigma.. = 3 grain boundary. 8 figs.
- Research Organization:
- Arizona Univ., Tucson (USA)
- DOE Contract Number:
- FG02-87ER45285
- OSTI ID:
- 6936427
- Report Number(s):
- DOE/ER/45285-2; ON: DE89000026
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM
GRAIN BOUNDARIES
BICRYSTALS
COMPUTERIZED SIMULATION
EQUATIONS
EQUILIBRIUM
GRAIN ORIENTATION
INTERFACES
MELTING
PHASE TRANSFORMATIONS
PROGRESS REPORT
TRANSMISSION ELECTRON MICROSCOPY
CRYSTAL STRUCTURE
CRYSTALS
DOCUMENT TYPES
ELECTRON MICROSCOPY
ELEMENTS
METALS
MICROSCOPY
MICROSTRUCTURE
ORIENTATION
POLYCRYSTALS
SIMULATION
360102* - Metals & Alloys- Structure & Phase Studies