Atomistic simulations of dislocation mobility in Al, Ni and Al/Mg alloys
By D. L. Olmsted, Louis G. HectorJr., W. A. Curtin, R. Clifton. 2004
314 citations recorded by the source corpus.
Dislocation velocities and mobilities are studied using molecular dynamics simulations for edge and screw dislocations in pure aluminium and nickel, and edge dislocations in Al–2.5%Mg and Al–5.0%Mg random substitutional alloys using EAM potentials. In the pure materials, the velocities of all dislocations are close to linear with the ratio of (applied stress)/(temperature) at low velocities consistent with phonon drag models, and quantitative agreement with the experiment is obtained for the mobility in Al. At higher velocities, different behaviour is observed. The edge dislocation velocity remains dependent solely on (applied stress)/(temperature) up to approximately 1.0 MPa K−1, and approaches a plateau velocity that is lower than the smallest ‘forbidden’ speed predicted by continuum models. In contrast, above a velocity around half of the smallest continuum wave speed, the screw dislocation damping has a contribution dependent solely on stress with a functional form close to that predicted by a radiation damping model of Eshelby. At the highest applied stresses, there are several regimes of nearly constant (transonic) velocity separated by velocity gaps in the vicinity of forbidden velocities; various modes of dislocation disintegration and destabilization were also encountered in this regime. In the alloy systems, there is a temperature- and concentration-dependent pinning regime where the velocity drops sharply below the pure metal velocity. Above the pinning regime but at moderate stresses, the velocity is again linear in (applied stress)/(temperature) but with a lower mobility than in the pure metal.
Subfields: Materials Chemistry, Physical and Theoretical Chemistry
View Paper: https://www.semanticscholar.org/paper/12106df89ef57461ce8048e9933647e46927ae97
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In Materials Chemistry
Citations in the corpus
- Multiscale modeling of the plasticity in an aluminum single crystal (2009, methodology): “In this work, the value of this parameter is computed using MD simulations (Daw et al., 1993; Olmsted et al., 2005) for the motion of a single dislocation in a pure aluminum single crystal.”