Modelling the Influence of Dynamic Strain Ageing on Deformation Behaviour

A model for the flow stress of low-alloy steels is presented. In addition to work hardening and dynamic recovery the model includes dynamic strain ageing. Special attention is paid to the validity of the model at larger strains and to the mutual relationship between work hardening, dynamic recovery and dynamic strain ageing. This leads to a model consisting of three evolution equations, one for each of the three state variables, being the free dislocation density, the locked dislocation density and the free solute density. The model is consistent with previous work on work hardening at low temperatures. The model was applied to austenite. Experiments have been performed to measure the flow stress of austenite as a function of the strain rate and temperature. The dependence of the flow stress on temperature and strain rate has been investigated for various low-alloy steels. It can be explained by assuming climb of dislocations by bulk diffusion of vacancies as the appropriate mechanism. The relation between the coefficients in the model and the chemical composition is analysed and discussed.