Masters Theses

Alternative Title

Computer simulation of radiation damage in iron aluminide

Abstract

"A computer program, designed to simulate the ordered state of the B.C.C. alloy, Fe₃Al, was used to study the effects of irradiation on an order-disorder alloy. Twenty-six runs were made with this program representing a variety of initial conditions. In all cases, the final damaged state consisted of Frenkel defects, vacancy-interstitial pairs; and the distance separating these pairs was a sensitive function of the energy and direction imparted to the primary knock-on. Both the vacancy and the interstitial were found to be normal, stable defects, with the interstitial residing in a "split"-configuration oriented in the [110] direction. The threshold energies for permanent atomic displacement were also found to be strongly directionally dependent. The [100] direction proved to have the lowest threshold with a value of 22 eV (for a chain of all Fe atoms) for the directions studied. The threshold for the [110] direction was about 44 eV, while that for the [111] direction was not determined because of its very complex behavior. "Replacement chains" were prevalent in the [100] and the [110] directions. After an initial energy loss of about 10 to 15 eV, the replacement chains progressed with relatively little loss of energy per atomic collision. "Focusons" were also prevalent and served as the primary mechanism for dissipating energy from the collision chain. This mechanism was operative in the [100] and [lll] directions and was especially noticeable during the "defocusing" collisions. The defocusing replacement chains were introduced at energies of about 110 eV and knock-on directions from 1 to 1.5' away from the [100] and [111] directions. The energy dissipation along a defocused chain closely resembled the "thermal spike" concept; while, the extensive expansion of the lattice near the end of the defocused chain (especially in the [111] direction) was reminiscent of a "plasticity spike." The presence of aluminum atoms had a strong influence on several of the dynamic events. The small mass of the aluminum atoms present in the [lll] chain impeded the progress of the replacement chain; while, the defocusing in the [100] and [111] directions was enhanced by the aluminum's low mass and high mobility. Disordering was found to be most significant in the defocused chains. The [100] and [110] replacement chains containing all iron atoms showed no disordering when the iron atoms exchanged places. Since the aluminum atoms were not replaced in either the [111] direction or the [100] (alternate iron and aluminum atoms) direction, no disordering occurred. The disordering in the defocused chains arose from the general mixing of the lattice atoms along the chain especially in the "plasticity spike" region"--Abstract, page ii-iv.

Advisor(s)

Leighly, Hollis P., 1923-2004

Committee Member(s)

Edwards, D. R.
Hill, Otto H.

Department(s)

Nuclear Engineering and Radiation Science

Degree Name

M.S. in Nuclear Engineering

Publisher

University of Missouri at Rolla

Publication Date

1968

Pagination

ix, 106 pages

Note about bibliography

Includes bibliographical references (pages 85-88), footnotes (pages 82-84) and index (pages 89-97).

Rights

© 1968 Roland Otto Jackson, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Subject Headings

Iron-aluminum alloys -- Effect of radiation onOrder-disorder in alloysRadiation -- Simulation methods

Thesis Number

T 2122

Print OCLC #

5995639

Electronic OCLC #

805723850

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