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Dislocation drag in close-packed metals

Vreeland, Thad, Jr. (1984) Dislocation drag in close-packed metals. Scripta Metallurgica, 18 (7). pp. 645-651. ISSN 0036-9748. doi:10.1016/0036-9748(84)90313-2.

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The observation of dislocation displacements produced by stress pulses of controlled amplitude and duration has been used to deduce the dislocation drag force in close-packed metals. This paper summarizes the experimental techniques developed at the California Institute of Technology to make drag force measurements in single crystals of zinc, copper, and aluminum, and compares the measurements made by these techniques with current theories of dislocation drag. Prior to any drag measurements in close-packed metals, it had been shown that slip bands grew with macroscopically uniform velocities in LiF (1), silicon-iron (2), Si (3), NaCl (4), Ge (5), and W (6) when subjected to a constant applied resolved shear stress. The slip bands formed where "fresh" dislocations had been produced by local surface damage (point loading or scratching). Dislocations produced by the local damage were observed by etch pit techniques prior to applying the stress, and the slip bands were revealed by re-etching after the stress was removed. The average velocity of the leading dislocations in the slip bands was much less than 1 cm/s at the initial flow stress in these materials. The initial attempts to measure dislocation velocities in the basal slip system of HCP zinc (7) using a rapid loading system to produce stress pulses met with an experimental difficulty. Dislocations often traversed the entire crystal during the minimum duration stress pulse (17 ms) indicating velocities in excess of 1 cm/s at the initial flow stress. The large difference in dislocation mobility in HCP zinc and the BCC and ionic or covalent crystals was investigated using newly developed techniques of stress pulse loading and dislocation observation which are described in the following section.

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Additional Information:© 1984 Pergamon Press Ltd. Received March 9, 1984.
Issue or Number:7
Record Number:CaltechAUTHORS:20150304-080034581
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Official Citation:Thad Vreeland Jr., Dislocation drag in close-packed metals, Scripta Metallurgica, Volume 18, Issue 7, July 1984, Pages 645-651, ISSN 0036-9748, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:55497
Deposited By: Tony Diaz
Deposited On:04 Mar 2015 22:21
Last Modified:10 Nov 2021 20:46

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