Abstract
The stability and mobility of active slip systems in superlattice structures, for both cubic and noncubic crystals, are theoretically investigated based on the energetics and kinetics of dislocation dissociations. The main concept of the force couplet model for the positive temperature dependence of yield and flow stress is introduced. Two sources of the glide resistance in ordered lattices are the fault dragging mechanism and the cross-slip pinning mechanism. The effective fault energy consists of two terms related to the chemical and mechanical instability of a shear fault (APB or SISF). Dependence of the yield stress on the orientation and the sense of applied stress stems from the signs and magnitudes of the glide and non-glide stresses. As the effective fault energy is altered by solute segregation and/or high non-glide stress, the two glide resistance mechanisms are affected differently. In Ni 3Al and β-CuZn, the anomalous yield strength, strian rate sensitivity, in situ deformation TEM observations, and nonstoichiometry effect are discussed in view of the present model.
Published Version
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