Molecular dynamics study of thermal disorder in a bicrystal model

Technical Report · Thu Sep 01 04:00:00 EDT 1988

OSTI ID:6338490

Nguyen, Tue

The question of whether or not the grain boundary (gb) interface will melt at a temperature distinctly below the bulk melting point T/sub m/ has been longstanding. Experiments have shown that there is no evidence of gb premelting but resolution limitations preclude detailed observations of the onset of thermal disordering at the gb before it melts. Molecular dynamics (MD) simulation results regarding this question of gb premelting are divided, because techniques and models have been used. This thesis attempts to resolve this issue by a careful MD study of a (310) theta = 36.86/degree/ <001> symmetrical tilt bicrystal model using an Embedded Atom Method (EAM) aluminum potential. The melting temperature T/sub m/ is first determined using the criterion of coexistence of the solid and liquid phases. Then the gb structure is studied directly to determine whether or not there is gb premelting. Finally, the thermal disorder behavior of the gb structure below melting is examined. Based on the explicit results concerning structural order, energy and mobility obtained from the present simulations, we find that our bicrystal model shows no evidence of premelting (complete melting below T/sub m/). Both the surface and the gb interface exhibit thermal disorder at temperatures below T/sub m/ with complete melting occurring at or very near T/sub m/. Concerning the details of the onset of melting, the data show considerable disordering in the interfacial region starting at about 0.93 T/sub m/. 83 refs., 119 figs., 9 tabs.

• Research Organization: Massachusetts Inst. of Tech., Cambridge (USA)
• DOE Contract Number: AC05-76OR00033
• OSTI ID: 6338490
• Report Number(s): DOE/OR/00033-T420
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals &amp; Alloys-- Structure &amp; Phase Studies
360204 -- Ceramics
Cermets
&amp; Refractories-- Physical Properties
ALUMINIUM
BICRYSTALS
COMPUTERIZED SIMULATION
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
CRYSTALS
DIFFUSION
DIMENSIONS
ELEMENTS
ENERGY
GRAIN BOUNDARIES
HIGH TEMPERATURE
INTERFACES
MATHEMATICAL MODELS
MELTING
MELTING POINTS
METALS
MICROSTRUCTURE
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POINT DEFECTS
POLYCRYSTALS
POTENTIAL ENERGY
SIMULATION
THERMODYNAMIC PROPERTIES
THICKNESS
TRANSITION TEMPERATURE
VACANCIES