Phänomenologische Modellierung des Warmfließverhaltens einer Nickel-Basis-Legierung

To model the hot deformation behaviour of a NiCrMoFe alloy the phenomenological Sellars model was applied to a set of high temperature flow curves. The flow curves were available for temperatures of 800-1200°C (in steps of 100°C) and strain rates of 0.1/s, 0.5/s, 1/s and 5/s and a maximal true strain of 1. Some of these curves show a typical hardening and recovery progression while others show a drop in flow stress associated with the onset of recrystallisation. Therefore, the model was parameterised independently for recovery and recrystallization type curves. The model was adapted for each single curve and the determined parameters were plotted against the Zener-Hollomon parameter. Conditional equations could be derived from these plots. Recovery and recrystallisation type flow curves can be modelled with satisfying accuracy. Different sets of hardening parameters are necessary for recovery and recrystallisation type flow curves. Thus a criterion is needed to decide whether a recovery or a recrystallisation flow curve type has to be assumed. It is shown that the Zener-Hollomon parameter is an adequate choice.