Predictive Modelling of Mechanical Properties of Materials for Fusion Power Plants

Completed

Nuclear Fission and Fusion(Nuclear Fusion)

Basic and strategic applied research

PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials)

Not Cross-cutting

Professor MW Finnis
Materials
Imperial College London

Standard

EPSRC

01 January 2005

31 December 2008

48 months

£165,917

Mechanical engineering

London

Metals and alloys -- Materials, Mechanical and Medical Eng

Professor MW Finnis, Materials, Imperial College London

Project Contact, EURATOM/CCFE

This research project is aimed at a thorough understanding of the microstructure, flow and fracture behaviour of metals and alloys with the the body-centred cubic crystal structure. The specific focus is on materials proposed for structural components in fusion power plants; vanadium and tungsten, iron and iron-chromium binaries up to 12% Cr. The project will also examine the changes in behaviour of the materials produced by irradiation. The understanding achieved in the project will enable us to predict the mechanical behaviour of these and related materials. The approach is to use inter-linked computer modelling methods, at scales ranging from the sub-atomic to that of the materials' microstructure. Each level will use input parameters derived from more fundamental levels of modelling. The key elements are (a) abinitio modelling for development of interatomic potentials for use in molecular dynamics (MD) simulations; (b) MD modelling of (i) defect generation under high-energy neutron irradiation, (ii) dislocation mobility in defect-free crystals of the materials and (iii) interactions of dislocations with defects; (c) kinetic theory and kinetic Monte-Carlo modelling of evolution of collision cascade structures beyond the MD timescale; (d) dislocation dynamics simulations of flow, fracture and brittle - ductile transition behaviour. This modelling project will be closely linked to a complementary experimental programme (-750k) funded by UKAEA Culham, which will act to guide development of the models and to verify their predictions.

This research project was aimed at a thorough understanding of the microstructure, flow and fracture behaviour of metals and alloys with the body-centred cubic crystal structure. The specific focus was on materials proposed for structural components in fusion power plants; vanadium and tungsten, iron and iron-chromium binaries up to 12% Cr. The project also examined the changes in behaviour of the materials produced by irradiation. The understanding achieved in the project provides a fundamental insight into the origins of the mechanical behaviour of these and related materials. The approach used inter-linked computer modelling methods, at scales ranging from the sub-atomic to that of the materials' microstructure. Each level employed input parameters derived from more fundamental levels of modelling. The modelling project was closely linked to a complementary experimental programme funded by UKAEA Culham, which guided development of the models and checked their predictions. The key results were : (a) robust interatomic potentials for the non-magnetic bcc metals (V,W) and for magnetic bcc metals and alloys (Fe,Cr,and Fe-Cr) were developed and fitted to a high-throughput ab-initio data base ; (b) molecular dynamics (MD) simulations using these potentials investigated the type and density of defects in high-energy collision cascades, the stress and temperature dependence of the mobility of screw and edge dislocations, and dislocation interactions with defects under irradiation; (c ) Monte Carlo (MC) simulations using ab-initio many-body expansions for the energy modelled clustering in the magnetic Fe-Cr system and found a change in sign of the short-range order parameter at about 10% Cr in good agreement with experiment; (d) dislocation dynamics (DD) models were successfully developed that accurately predicted the experimental brittle-ductile transitions, and the strengths of dislocation -radiation damage interactions, in W and Fe-Cr alloys. (e) radiation damage -induced dislocation loops produced by ion-irradiation of Fe and Fe-Cr specimens were of types predicted by modelling.

01/01/07