期刊
ACTA MATERIALIA
卷 61, 期 4, 页码 1394-1403出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2012.11.016
关键词
Fracture; Dislocations; Crack-dislocation interaction; Brittle-to-ductile transition; Atomistic simulations
资金
- German Science Foundation (DFG) [Gu 367/30, HO 2187/6-1]
- KITP
- Materials Department, UC Santa Barbara through NSF [PH11-25915, DMR-0843934]
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0843934] Funding Source: National Science Foundation
Whether a stressed material fractures by brittle cleavage or ductile rupture is determined by its ability to convert elastic strain energy to plastic deformation through the generation and motion of dislocations. Although it is known that pre-existing dislocations play a crucial role in crack tip plasticity, the involved mechanisms are unclear. Here it is demonstrated by atomistic simulations that individual pre-existing dislocations may lead to the generation of large numbers of dislocations at the crack tip. The newly generated dislocations are usually of different types. The processes involved are fundamentally different for stationary cracks and propagating cracks. Whereas local crack front reorientation plays an important role in propagating cracks, the multiplication mechanism at stationary cracks is connected with cross-slip in the highly inhomogeneous stress field of the crack. Analysis of the forces acting on the dislocations allows to determine which dislocations multiply and the slip systems they activate. These results provide the necessary physical link between pre-existing dislocations and the generation of dislocations at crack tips. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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