Atomistic simulations of Paidar-Pope-Vitek lock formation in Ni 3Al

Abstract

The thermally activated process of Paidar-Pope-Vitek (PPV) lock formation in the L1 2 intermetallic Ni 3Al is simulated using the "nudged elastic band" method with an embedded atom potential. It is found that the one-step PPV lock is intrinsically unstable, but it can be stabilized by a large enough Escaig stress. The two-step PPV lock can be formed with a low activation energy when the one-step lock is involved as an intermediate step. In this case, the overall activation energy is about 1 eV, in reasonable agreement with the range of 0.5-0.9 eV expected from experimental observation of the flow stress anomaly in Ni 3Al. High Escaig stresses are required to stabilize the one-step lock, and the absence of such high stresses in the micro-strain regime is thought to be the underlying reason for the absence of the flow stress anomaly in micro-strain conditions. © 2003 Elsevier B.V. All rights reserved.