FE² scheme for simulation of thermo-mechanically induced phase transformations and residual stresses in Ti6A14V components

To gain a physical based understanding of the evolution of micro-scale heterogeneities and residual stresses in Ti6Al4V components, a fully coupled three-dimensional multi-length scale and multi-physics finite element based model is introduced. Each integration point of the macro-scale model is coupled with a periodic micro-field model providing temperature and displacement degrees of freedom on both length scales utilising a nested corotational updated Lagrangian solution scheme suitable for small-and large-strain problems. Processing conditions as they appear during forging or heat treatment for instance are applied to the macro-scale model representing the investigated component, whereas the attached micro-scale models provide the constitutive behaviour and display the microstructure evolution. The deformation gradient and temperature gradient at each macro-scale integration point are applied as boundary conditions to the spatially periodic micro-scale models in a sophisticated way to obtain the consistent stress and heat flux update via volumetric homogenisation techniques. The required macroscopic material properties are derived via a sophisticated micro-scale testing procedure.