A Multiscale Model of Creep in Steels with Account for the Microstructure

A multiscale model has been developed to describe the influence of microstructure and content of alloying elements on the rate of radiation creep in EP823 and EK164 steels. A scheme is proposed for modeling the motion of dislocations and the interaction of dislocations with point defects within the molecular dynamics method in real alloys containing loops, pores, and precipitates with characteristic sizes and composition determined experimentally. Disordered Fe-based solid solutions of Cr and Cr + Ni corresponding to the specifications of EP 823 and EK 164 steels are used as a matrix. The evolution of the local dislocation density in the grain is calculated using the method of discrete dislocation dynamics, taking into account the dislocation climb and slip. It is shown that the local dislocation density changes with the formation of a microstructure. The distribution of local stresses in the lattice caused by the microstructure is calculated. The creep rate values in FeCr and FeCrNi alloys are calculated taking into account the presence of microstructure. The creep rate values obtained as a result of modeling differ from measured values by 20–50%. Factors limiting the accuracy of the model are revealed, and a modeling algorithm is proposed to improve the accuracy of creep rate prediction.