9 research outputs found
A Micromechanical Model of Hardening, Rate Sensitivity and Thermal Softening in BCC Single Crystals
The present paper is concerned with the development of a micromechanical
model of the hardening, rate-sensitivity and thermal softening of bcc crystals.
In formulating the model we specifically consider the following unit processes:
double-kink formation and thermally activated motion of kinks; the close-range
interactions between primary and forest dislocations, leading to the formation
of jogs; the percolation motion of dislocations through a random array of
forest dislocations introducing short-range obstacles of different strengths;
dislocation multiplication due to breeding by double cross-slip; and
dislocation pair annihilation. The model is found to capture salient features
of the behavior of Ta crystals such as: the dependence of the initial yield
point on temperature and strain rate; the presence of a marked stage I of easy
glide, specially at low temperatures and high strain rates; the sharp onset of
stage II hardening and its tendency to shift towards lower strains, and
eventually disappear, as the temperature increases or the strain rate
decreases; the parabolic stage II hardening at low strain rates or high
temperatures; the stage II softening at high strain rates or low temperatures;
the trend towards saturation at high strains; the temperature and strain-rate
dependence of the saturation stress; and the orientation dependence of the
hardening rate.Comment: 27 pages (LaTeX) and 15 Figures (jpg