Doctoral Dissertations

Abstract

"The kilocycle range dislocation damping and Young's modulus of single crystals of magnesium and single crystals of magnesium containing small additions of lithium, zinc, or aluminum have been studied as a function of strain amplitude, temperature, and time during annealing and following a high strain amplitude vibration. The data are compared to the Granato-Lücke theory of dislocation damping, the Granato-Hikata-Lücke theory for the recovery of damping following plastic deformation, and the Yamafuji-Bauer theory for the recovery of damping following a high strain amplitude vibration. Reasonable qualitative agreement is obtained between the Granato-Lücke theory and the observed dependence of the damping and modulus on strain amplitude and temperature. Reasonable quantitative values for the dislocation density, network node loop length, and activation energy for the migration of vacancies in magnesium are obtained. It is found that in order to get agreement with the decay of the damping during annealing at high temperature, it is necessary to modify the Granato-Hikata-Lücke theory. This is accomplished by replacing the Cottrell-Bilby expression for the segregation of pinning points to dislocations by an expression suggested by Harper to account for longer times. The observed dependence of the damping on composition does not agree with the Granato-Lücke predictions. A possible explanation for this discrepancy is offered. Several new phenomena that were observed are described and discussed"--Abstract, page i..

Advisor(s)

Brown, Harry A., 1925-1995

Committee Member(s)

Furlong, LeRoy R.
Fuller, Harold Q., 1907-1996
Lund, Louis H., 1919-1998
Johnson, Charles A.

Department(s)

Physics

Degree Name

Ph. D. in Physics

Sponsor(s)

United States. Bureau of Mines

Publisher

University of Missouri at Rolla

Publication Date

1967

Pagination

xiv, 112 pages

Note about bibliography

Includes bibliographical references (pages 104-106).

Rights

© 1967 Robert Ray Nothdurft, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Dislocations in crystals
Magnesium alloys -- Microstructure

Thesis Number

T 2039

Print OCLC #

5988085

Electronic OCLC #

781286887

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