Quantifying internal stress and internal resistance associated with thermal ageing and creep in a polycrystalline material

In situ neutron diffraction combined with the incremental deformation at room temperature has been used to provide a measure of the internal stress and internal resistance generated by prior inelastic deformation at high temperature in an austenitic stainless steel. Interactions between the internal stress and internal resistance are considered explicitly by using the proposed measurement technique. The magnitude of the intergranular internal stress is found to be a function of the total inelastic strain created by prior high temperature deformation. The deviation from linearity observed in the lattice strain response is used to derive the microscopic internal resistance, but a crystal plasticity model is required to infer the absolute value. The macroscopic internal resistance is shown to be consistent with Taylor hardening. A refined internal state concept is proposed based on the Kocks-Mecking model to provide a further step to predict the inelastic deformation.