Constriction energy in the presence of a solute field

It has been widely known that both solute concentration, i.e., frictional effects, and stacking fault energy influence the degree of cross slip and slip planarity in face-centered-cubic alloys. Cross slip is preceded by constriction of two partial dislocations. A model is proposed for the energy required to form a constriction from two parallel partial dislocations as a function of stacking fault energy, solute concentration, atomic size misfit, and modulus mismatch. The cross slip is curtailed due to interaction of solute atoms with the partials. Both the atomic size misfit and modulus mismatch influence the local solute concentration which introduce local stresses that determine the energy needed to form the constriction. The shape of partials and the energy to form the constriction was established for stacking fault energies in the range of 10-100 mJ/m(2), misfit strains in the range of 0.1-0.5, modulus mismatch levels of -1.0, and nominal solute concentrations varying from 0 to 10 at. %. In extreme cases, the constriction energy has been found to increase fourfold compared to the solute-free case. The modulus mismatch effect is important in substitutional alloys with small misfit strains (< 0.1) while for interstitial solute cases the misfit strain effects dominate. The results converge to the well-known solution of Stroh in the limit of zero solute concentration. (C) 2000 American Institute of Physics. [S0021-8979(00)04905-7].