Temperature dependent dislocation bypass mechanism for coherent precipitates in Cu-Co alloys

Title
Temperature dependent dislocation bypass mechanism for coherent precipitates in Cu-Co alloys
Authors
심재혁이현지Brian D. Wirth
Keywords
Cu-Co; Dislocation; Critical resolved shear stress; Molecular dynamics; Bypass mechanism; Precipitate; Stacking fault
Issue Date
2016-05
Publisher
Acta materialia
Citation
VOL 110, NO 1, 276-282
Abstract
Molecular dynamics simulations of dislocation interaction with coherent cobalt precipitates embedded in Cu– Co alloys reveal a temperature dependent bypass mechanism. Below 300 K, the trailing partial dislocation clearly bypasses the coherent, face centered cubic (FCC) cobalt precipitate by Orowan looping, caused by a reversible structural transformation as the leading partial locally converts the precipitate to the lower-energy hexagonal close packed (HCP) structure. The FCC versus HCP energy difference of cobalt is temperature dependent, and the dislocation bypass mechanism becomes pure shear above 300 K. Based on a combination of inertial effects due to phonon drag and this observed bypass mechanism, we develop a temperature dependent critical resolved shear stress (CRSS) model, which is in excellent agreement with long-standing measurements of the CRSS temperature dependence of Cu– Co alloys, and those obtained from MD simulation. The model explains both the CRSS increase at low temperatures and the existence of a peak value around 200 K.
URI
http://pubs.kist.re.kr/handle/201004/59152
ISSN
13596454
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