Abstract
It is well known that, under plastic deformation, dislocations are not only created but also move through the crystal, and their mobility is impeded by their interaction with the crystal structure. At high stress and temperature, this “drag” is dominated by phonon wind, i.e., phonons scattering off dislocations. Employing the semi-isotropic approach discussed in detail in a previous paper (J. Phys. Chem. Solids 2019, 124, 24–35), we discuss here the approximate functional dependence of dislocation drag B on dislocation velocity in various regimes between a few percent of transverse sound speed and (where is the effective average transverse sound speed of the polycrystal). In doing so, we find an effective functional form for dislocation drag for different slip systems and dislocation characters at fixed (room) temperature and low pressure.
Highlights
Many modern material strength models, for example those in Refs. [1,2,3,4,5,6,7], are based on dislocation dynamics
At temperatures comparable to or higher than the Debye temperature and at high stress, phonons scattering off dislocations
In Ref. [13], the theory developed by Alshits and collaborators [15] is taken to the level by including the full velocity dependence of B, and longitudinal phonons as well as an anisotropic dislocation field and single crystal elastic constants. This model developed having polycrystals in mind, keeps the phonon spectrum isotropic, but dislocations are modeled according to the single crystal symmetry in order to take into account their anisotropy to some extent
Summary
Many modern material strength models, for example those in Refs. [1,2,3,4,5,6,7], are based on dislocation dynamics. [13], the theory developed by Alshits and collaborators [15] is taken to the level by including the full velocity dependence of B, and longitudinal phonons (in addition to the dominating contribution of transverse phonons) as well as an anisotropic dislocation field and single crystal elastic constants. This model developed having polycrystals in mind, keeps the phonon spectrum isotropic (for simplicity), but dislocations are modeled according to the single crystal symmetry (bcc, fcc, hcp, etc.) in order to take into account their anisotropy to some extent. The current work in a sense complements Ref. [13] and the theory developed there
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