Effect of Dislocation Character on the CRSS

The yield strength of a crystalline structural material is a fundamental mechanical property predominantly governed by the critical stress for dislocation slip. This Critical Resolved Shear Stress (CRSS) is strongly influenced by the character of the dislocation (e.g., screw, edge, or mixed) as shown in previous experimental studies. Existing analytical approaches for CRSS prediction assume an atomic row description of the slip plane and do not account for Wigner-Seitz (WS) cell area at each discrete lattice site. Further, inadequate consideration of the material`s elastic anisotropy and the presumed dislocation “core-width” level precludes correct CRSS determination. This study proposes a predictive model applied to Face Centered Cubic (FCC) materials addressing these shortcomings in predicting glide stress of a dissociated dislocation. The core-width is rigorously determined from the minimization of total energy comprised of continuum strain energy ( E S T R A I N ) and atomistic misfit energy ( E M I S F I T ) of the dislocation`s core. The E S T R A I N is obtained from dislocation strain-fields calculated using the fully-anisotropic Eshelby-Stroh formalism. The E M I S F I T is determined from the Generalized Stacking Fault Energy (GSFE) landscape of the slip plane. Previous E M I S F I T calculations are restricted to slipped rows in ‘simple’ cubic lattices which do not represent the slip-planes in FCC crystals. The developed model is used to predict CRSS for a wide range of metallic materials correcting the overprediction of experimental CRSS levels. The results unveiled the remarkable dependence of CRSS on the dislocation character, revealing the non-trivial dependence on GSFE parameters. Thus, this study addresses a major void in structure-property prediction for structural materials.