Evolution of phase stresses in Al/SiCp composite during thermal cycling and compression test studied using diffraction and self-consistent models

In this work, the evolutions of stresses in both phases of the Al/SiCp composite subjected to thermal cycling during in situ compression test were measured using Time of Flight neutron diffraction. It was confirmed that inter-phase stresses in the studied composite can be caused by differences in the coefficient of thermal expansion for the reinforcement and matrix, leading to a different variation of phase volumes during sample heating or cooling. The results of the diffraction experiment during thermal cycling were well predicted by the Thermo-Mechanical Self-Consistent model. The experimental study of elastic-plastic deformation was carried out in situ on a unique diffractometer EPSILON-MDS (JINR in Dubna, Russia) with nine detector banks measuring interplanar spacings simultaneously in 9 orientations of scattering vector. For the first time, the performed analysis of experimental data allowed to study the evolution of full stress tensor in both phases of the composite and to consider the decomposition of this tensor into deviatoric and hydrostatic components. It was found that the novel Developed Thermo-Mechanical Self-Consistent model correctly predicted stress evolution during compressive loading, taking into account the relaxation of thermal origin hydrostatic stresses. The comparison of this model with experimental data at the macroscopic level and the level of phases showed that strengthening of the Al/SiCp composite is caused by stress transfer from the plastically deformed Al2124 matrix to the elastic SiCp reinforcement, while thermal stresses relaxation does not significantly affect the overall composite properties.