A physically-based constitutive model for high temperature microstructural degradation under cyclic deformation

This paper presents a dislocation-mechanics cyclic viscoplasticity model which incorporates the key physical micro-mechanisms of strengthening and softening for high temperature deformation of 9Cr steels. In particular, these include precipitate and grain boundary strengthening, low-angle boundary dislocation annihilation and martensitic lath width evolution, using dislocation density as a key variable. The new model is applied to P91 steel across a range of strain-rates and strain-ranges in the 400-600 C temperature range, for power plant header applications, to demonstrate the effect of key microstructural parameters on high temperature low cycle fatigue performance. (C) 2017 Elsevier Ltd. All rights reserved.This publication has emanated from research conducted with the financial support of Science Foundation Ireland under Grant Numbers SFI/14/IA/2604 and SFI/10/IN.1/I3015. The authors would also like to acknowledge the contributions made by the collaborators of the METCAM and MECHANNICS projects, including Prof. Noel O’Dowd and Dr. Brian Golden of the University of Limerick, Ms. Eimear O’Hara of NUI Galway, Prof. Dongfeng Li of Shenzen Graduate School (formerly of NUI Galway), Dr. Christopher Hyde of the University of Nottingham and Dr. Tadhg Farragher (formerly of NUI Galway).peer-reviewe