Effect of non-glide componenets of the stress tensor on deformation behavior of BCC transition metals

摘要

In this paper we demonstrate by atomic computer simulaton that the non-Schmid slip behavior in bcc metals is a direct consequence of the non-planar core structure of 1/2<111>screw dislocations and the their response to the applied stress tensor. The analysis has been carried out in detail for tantalum using the FInnis-Sinclair type central force manypbody potentials. Two distinct non-Schmid effects have been discerned. The first is twinning-antiwinning slip asymmetry on {112} planes. This is an intrinsic property of the bcc structure and depends on the sense of the applied glide stress. The second non-Schmid effect is extrinsic and is controlled by the non-glide shear stresses perpendicular to the total Burgers vector on {110} planes into which the stress-free core of screw dislocations spread.