We propose to derive single crystal elastic constants on polycrystalline two-phase alloys by diffraction studies. Our main goal is to establish a method to determine elastic constants in technical multiphase alloys. In particular for materials which are not available as single crystals or in single phase forms this apprach would be highly beneficial. The proposed method required diffraction studies under various orientations of the load axis with respect to the incident beam. This can be achieved by our tensile rigs allowing an orientation of the load axis in a Eulerian cradle like way. We propose to carry out the investigations on diffractometer D20 or alternatively SALSA. The data will be analysed using the software package MAUD and by our own software.