Doctoral Dissertations

Abstract

"A detailed study of the deformation processes in sublimed magnesium under reverse bending fatigue in air at room temperature has been undertaken utilizing the light, scanning and transmission electron microscopy. The Principal deformation modes are the basal slip and {10Ī2} twinning. The proportion of twinning increases markedly with the increasing stress level and the number of cycles. The evidence for cross slip is seen on the basal slip bands. The extrusions are seen not only along the basal slip lines but also along the {10Ī2} twin boundaries. In the later stages of fatigue, the extrusions chip off producing a notch for the crack initiation. At low stress levels cracks initiate in the grain boundaries and propagate intergranularly. At high stress levels, cracks also nucleate at the intersections of the basal slip extrusion and {10Ī2} twins. The cracks also propagate transgranularly along the and prism planes and {10Ī2} twin boundaries. The transmission electron microscopy of the regions near the surface of the test bars, revealed patches of edge dislocation dipoles having Burgers vectors mainly parallel to one close packed direction. These dipoles appear to have formed by the double cross slip mechanism"--Abstract, Page ii.

Advisor(s)

Clark, J. B. (J. Beverley)

Committee Member(s)

Kreidl, N. J.
Frad, William A., 1909-1974
Wuttig, Manfred
Moore, Robert E., 1930-2003

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Metallurgical Engineering

Publisher

University of Missouri--Rolla

Publication Date

1970

Pagination

xi, 104 Pages

Note about bibliography

Includes bibliographical references (Pages 99-103).

Rights

© 1970 Babu Narain Thakur, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Metals -- FatigueDeformations (Mechanics) -- TestingMagnesium -- Metallurgy

Thesis Number

T 2411

Print OCLC #

6023633

Electronic OCLC #

846662890

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