期刊
ACTA MATERIALIA
卷 58, 期 9, 页码 3504-3515出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2010.02.024
关键词
Iron; Dislocation mobility; Plastic deformation; Thermally activated mechanisms
资金
- European Fusion Development Agreement
In situ straining experiments have been carried out at low temperature in pure Fe, in order to study the change of mechanism occurring at around 250 K. The local stress necessary to move individual screw dislocations is in good agreement with the macroscopic yield stress at various temperatures. In the lower temperature range, straight screw segments have a jerky motion in {1 1 0} planes, at variance from the steady motion observed near room temperature. The distributions of waiting times in locked positions, and jump distances, the temperature variation of the average jump distance, and the stress/temperature variation of the macroscopic activation areas, are inconsistent with the kink-pair mechanism observed above 250 K. They have been interpreted in terms of a locking-unlocking mechanism, already proposed in hexagonal-closed-packed metals. Under such conditions, the change of mechanism at 250 K can account for the surprisingly low value of the flow stress extrapolated to 0 K (much lower than the theoretical Peierls stress). (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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