Cross-slip of superpartial dislocations in iron aluminides

A simple model of the cross-slip of the 1/2 [111] superpartials in B2 intermetallics is analysed with the purpose of evaluating the importance of this mechanism for explanation of the anomalous flow stress increase in iron aluminides. The orientation dependence of the forces that act on the fractional dislocations of the threefold-split screw superpartials in the bcc-based lattice owing to the uniaxial tensile stress is studied. A critical stress necessary to keep the dislocation in motion is calculated as the stress under which the locking of the superpartial is equally probable as its unlocking. It is concluded that the cross-slip events play a significant role but it does not imply that other non-conservative dislocation processes can be ruled out.