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Addis Ababa University Libraries Electronic Thesis and Dissertations: AAU-ETD! >
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Thesis - Material Science >
Please use this identifier to cite or link to this item:
http://hdl.handle.net/123456789/3478
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| Title: | BRAGG-WILLIAMS MODEL OF ORDERED B2, L12 and L10 TYPE BINARY INTERMETALLIC COMPOUNDS CONTAINING POINT DEFECTS |
| Authors: | Daniel, G.Egziabher |
| Advisors: | Mulugeta Bekele(Dr.) |
| Keywords: | intermetallic compounds
nonstoichiometry |
| Copyright: | Apr-2011 |
| Date Added: | 25-Jul-2012 |
| Publisher: | Addis Ababa University |
| Abstract: | Ordered intermetallic compounds draw great interest at the present time because of both possible
applications and fundamental scientific importance. The scientific interest is derived from the
recognition that many intermetallics exhibit considerable ranges of nonstoichiometry which
correspond to the presence of constitutional point defects which are temperature independent.
Additional to these constitutional point defects thermally activated point defects can occur. The
total defect structure (i.e. the types and the concentrations of the point defects) determines
important properties of the intermetallic compounds (e.g. all diffusion dependent properties).
Hence, for understanding and control of these properties a detailed knowledge of the defect
structure in intermetallic compounds as function of composition and temperature within the
homogeneity range of the compounds is a prerequisite. This thesis is aimed at formulating a
model which can be used to calculating the ordering energy parameters ΔHAB and ΔHB□, and the
concentration of vacancy (z) and the concentration of Antistructure Defect as a function of the
composition parameter χ and the temperature T. The ordering energy is related to but different
from the formation energy, because the former is the energy change from the disordered alloy
AB to the ordered alloy AB, while the latter is the energy change from the pure metals A and B
to the ordered AB. Having obtained the model parameters (note that these are Hij and Sij for
the fitting of the vacancy concentration and hij and sij for the fitting of the thermodynamic
properties, respectively), the temperature dependence of the vacancy concentration can also be
determined. |
| Description: | A thesis submitted to the school of Graduate Studies
of Addis Ababa University in partial fulfilment of the
requirements for the degree of master of science in
Materials Science |
| URI: | http://hdl.handle.net/123456789/3478 |
| Appears in: | Thesis - Material Science
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