Diffraction analysis of internal strain-stress fields in textured transverserly-isotropic thin films: theoretical basis and simulation

Polycrystalline films produced via physical vapour deposition often possess a microstructure composed of columnar oriented grains. From the mechanical point of view, they cannot be treated as isotropic bulk solids; rather their elastic macroscopic behaviour is only transversely isotropic. In this context, the effect of texture on the elastic response of such films has been investigated for different grain interaction models. In particular, the determination of macroscopic stress by X-ray diffraction methods has been analysed. Traditional grain interaction models such as those due to Voigt and to Reuss have been compared with that proposed by Vook and Witt, compatible with the presence of only transverse isotropy of the body (even in the absence of crystallographic texture). By simulation, it has been demonstrated that, although texture only moderately affects the values of the macroscopic mechanical elastic constants of the transversely isotropic body, it can pronouncedly influence the results from the X-ray diffraction measurements. This effect is shown to depend strongly on the type of grain interaction.