Editing Plasticity (physics) (section)

==== Critical resolved shear stress dependence on temperature, strain rate, and point defects ====
[[File:Critical Resolved Shear Stress Versus Temperature.png|class=skin-invert-image|thumb|The three characteristic regions of the critical resolved shear stress as a function of temperature]]There are three characteristic regions of the critical resolved shear stress as a function of temperature. In the low temperature region 1 (''T'' ≤ 0.25''T''<sub>m</sub>), the [[strain rate]] must be high to achieve high ''τ''<sub>CRSS</sub> which is required to initiate dislocation glide and equivalently plastic flow. In region 1, the critical resolved shear stress has two components: athermal (''τ''<sub>''a''</sub>) and thermal (''τ''*) shear stresses, arising from the stress required to move dislocations in the presence of other dislocations, and the resistance of point defect obstacles to dislocation migration, respectively. At ''T'' =&nbsp;''T''*, the moderate temperature region 2 (0.25''T''<sub>m</sub>&nbsp;<&nbsp;''T''&nbsp;<&nbsp;0.7''T''<sub>m</sub>) is defined, where the thermal shear stress component ''τ''*&nbsp;→&nbsp;0, representing the elimination of point defect impedance to dislocation migration. Thus the temperature-independent critical resolved shear stress τ<sub>CRSS</sub> = τ<sub>a</sub> remains so until region 3 is defined. Notably, in region 2 moderate temperature time-dependent plastic deformation (creep) mechanisms such as solute-drag should be considered. Furthermore, in the high temperature region 3 (''T''&nbsp;≥&nbsp;0.7''T''<sub>m</sub>) έ can be low, contributing to low τ<sub>CRSS</sub>, however plastic flow will still occur due to thermally activated high temperature time-dependent plastic deformation mechanisms such as Nabarro–Herring (NH) and Coble diffusional flow through the lattice and along the single crystal surfaces, respectively, as well as dislocation climb-glide creep.