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Dislocation dynamics simulations of particle strengthening
Dislocation glide in a ductile matrix with particles of a secondary chemical phase is computer simulated. From these simulations the critical resolved shear stress (CRSS) is derived. The simulations are based on the local equilibrium of resolved stresses along the dislocations in one glide plane. Within this continuum-elastic approach, most accurate models are used. The elastic interaction of dislocations with each other and with themselves is fully allowed for (Brown 1964, Bacon 1967), i.e. no line tension is assumed. The spherical particles have a radius distribution and a spatial arrangement very close to that of a real Ostwald-ripened crys- tal. The dislocations glide in one plane (no cross-slip, no climb), but the interaction between particles and dislocations is modeled in three dimensions. Examples are given for dispersion strengthening, order strengthening and lattice mismatch strengthening. For some mechanisms, analytical expressions for the CRSS have been derived from the simulations. They contain no unknown parameters. The simulation results of lattice mismatch strengthening are compared to measurements on a corresponding real crystal. Further chances of dislocation dynamics simulations for particle strengthening are outlined.