SIMULATIONS OF FOREST INTERACTIONS AND STRAIN-HARDENING IN FCC CRYSTALS

The strain hardening properties of FCC single crystals are examined with the help of a three-dimensional simulation of dislocation dynamics and interactions at mesoscale. The basic properties discussed are the line tension of the dislocations, the conditions at which sessile junctions are formed at the intersection of two slip systems and the stability of these locks. The relation between the flow stress and the square root of the intersecting dislocation density is examined in areal glide and in multislip conditions. A validation of the model is performed by comparison with experimental results on copper single crystals. At the small strains reached by the simulation and in multislip conditions, strain hardening is found to originate from the continuous increase of forest density rather than from the formation of immobile loops around clusters of forest obstacles. It is suggested that at larger strains a stabilizing mechanism, possibly cross-slip, should enhance the dislocation storage processes and initiate the formation of dislocation cells.