A MODEL FOR THE ANOMALOUS MECHANICAL-PROPERTIES OF NICKEL-BASE L1(2) ORDERED ALLOYS .2. CROSS-SLIP PROCESSES AND MECHANICAL-PROPERTIES

A model based on the results of Part I, but taking into account more r ealistic cross-slip processes, is presented in this second part. It is based on a competition between two different cross-slip mechanisms on to the cube plane. Cross slip and glide over interatomic distances are shown to take place by a kink-pair (or double jog) mechanism, whereas cross slip and glide over larger distances are shown to take place by a cross-slip (or critical bow-out) mechanism. Assuming that the kink- pair mechanism is easier than the cross-slip mechanism, in agreement w ith microscopic observations, analytical expressions are obtained for the strain and temperature dependence of the yield-stress and strain-h ardening coefficient, which are in fairly good agreement with experime ntal results. The role of the complex stacking fault energy, the orien tation effects, and the tension-compression asymmetries, can be explai ned as in the PPV model. The stress-strain rate sensitivity and the re versibility of flow-stress upon a temperature decrease are also discus sed. Copyright (C) 1996 Acta Metallurgica Inc.