A dislocation-based model for high temperature cyclic viscoplasticity of 9–12Cr steels

• Published in: Computational materials science Vol. 92; pp. 286 - 297
• Main Authors: Barrett, R.A., O’Donoghue, P.E., Leen, S.B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.09.2014; Elsevier
• Subjects: Applied sciences; Chromium steels; Cyclic softening; Cyclic viscoplasticity; Dislocation density; Dislocations; Elasticity. Plasticity; Exact sciences and technology; Martensitic stainless steels; Mathematical models; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; P91 steel; Precipitate hardening; Precipitates; Precipitation; Viscoplasticity; Dislocation density; Precipitate hardening; Cyclic softening; Cyclic viscoplasticity; P91 steel; Heat treatment; Stress strain relation; Dislocation structure; High temperature; Precipitate; Elastoviscoplasticity; Precipitation hardening; Chromium steels; Kinematic hardening; Cyclic load; Size effect; Microstructure
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2014.05.034

[Display omitted] •Development of a dislocation-based cyclic softening model.•Development of a precipitate strengthening material model.•Prediction of microstructure size effects of laths and precipitates.•Application to 9–12Cr steels for different strain-rates and temperatures. A dislocation-based model for high temperature cyclic viscoplasticity in 9–12Cr steels is presented. This model incorporates (i) cyclic softening via decrease in overall dislocation density, loss of low angle boundary dislocations and coarsening of the microstructure and (ii) kinematic hardening via precipitate strengthening and dislocation substructure hardening. The effects of the primary micro-structural variables, viz. precipitate radii, dislocation density and martensitic lath width on cyclic viscoplasticity, reveal a size effect of initial precipitate radii and volume fraction, with smaller radii and a higher density of precipitate producing a stronger material. A similar effect is also predicted for initial martensitic lath width at temperatures below 500°C. The model is intended for microstructure sensitive design of high temperature materials and components for next generation power plant technology.