Thermal properties of polycrystals – X‐ray diffraction and scale transition modeling

The development of thermal residual stresses was investigated in polycrystalline materials. Two complementary ways were used: the experimental values obtained by X‐ray diffraction were compared to the results predicted by self‐consistent scale transition approaches. First, single‐phase materials were considered. The model was checked through the experimental study of rolled textured polycrystalline α‐Zr and α‐Ti with hexagonal closed packed structure. The level and the influence of the thermal stresses on the macroscopic behaviour have been quantified. In a second part, the model was extended to the case of two‐phase materials. A new approach was developed in order to characterize the coefficient of thermal expansion (CTE) of phases embedded in multiphase materials. The analysis of the problem was based on the coupling of numerical simulations with thermo‐elastic scale transition models and experiments. The whole approach was finally checked through the study of an Al‐50%vol.‐SiC‐50%vol. MMC. The CTE of Silicon Carbide were determined as a function of the temperature. Simulated results obtained show a very good agreement with experimental values available in the literature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)