We aim at modelling the effect of local phase-specific micro residual stresses on the residual stress evaluation for multiphase materials and plan to study the effect of local distributions of micro residual stresses on the lattice parameter D0. In this regard the generation of phase-specific residual stresses will be studied in detail for two fine grained duplex steels with varying content of the two dominant phases by means of neutron diffraction analysis of the load partitioning behavior. For this in-situ strain analysis will be carried out for cylindrical tension/compression samples using TOF neutron diffraction at ENGIN-X up to large plastic strain. Further, D0 will be determined for the same material states for small cuboid samples (sectioned by EDM) with variation in their cross section area. By this means the sample size effect on the D0 distribution will be analyzed. The samples