Mesoscale plastic texture in body-centered cubic metals under uniaxial load

Abstract

We develop a minimal continuum dislocation dynamics model for slip in bcc metals that accounts explicitly for non-Schmid behavior of screw dislocations in these materials. The dislocation substructure is represented by a continuum distribution of $1/2[111]$ screw dislocations moving on three possible ${110}$ planes according to the flow rule that describes the response of isolated screw dislocations to external loads. The cross-slip of dislocations is assessed using the master equation which takes into account different energy barriers for dislocations moving on the three slip planes. To demonstrate the performance of the model, we study the buildup of plastic strain at 77 K in both tension and compression for a number of loading directions covering the entire area of the standard stereographic triangle. The non-Schmid behavior of screw dislocations is shown to persist to the continuum level, whereby interactions between dislocations merely affect the rate of plastic flow.