Modelling the microstructural evolution of engineering materials

A continuum variational model has been developed to model the microstructural evolution of a general class of moving boundary precipitate systems within which elastic strain plays a significant role. The variational framework readily allows for the incorporation of a number of different competing kinetic processes and thermodynamic driving forces into a numerical model without geometrical restrictions. The driving forces considered here arise from compositional variations, interfacial energy, phase transformations and changes of elastic stored energy. The kinetic processes are lattice diffusion and interface migration.;The role of elasticity on the evolution of the microstructure is investigated with particular reference to how elastic fields influence the growth morphology of second-phase precipitates. The elasticity is considered in all phases and is assumed to be linear, isotropic but inhomogeneous. The types of elastic effects considered in this analysis arise from the misfit strain between the precipitate and matrix and an externally applied elastic field. The misfit strain has been shown to restrict the morphology of the growing precipitates and alter the equilibrium shape of precipitate particles from that observed in the absence of any elastic fields. In two-particle coarsening, long-range elastic interactions cause considerable particle shape changes.;Non-equilibrium conditions are modelled at the moving interface and mass conservation is satisfied as the interface translates. A static structured underlying grid is coupled with a dynamic unstructured finite element mesh which is adapted to fit the line of the moving boundary. When the finite element mesh is identified as being distorted, compositional data is transferred from one finite element geometry to another by mapping to and from the structured grid.