Measurement of the evolution of internal strain and load partitioning in magnesium hybrid composites under compression load using in-situ synchrotron X-ray diffraction analysis

Energy dispersive synchrotron X-ray diffraction analysis has been applied to evaluate the evolution of average internal elastic lattice strains under compression load within the phases of magnesium hybrid composites, reinforced by silicon-carbide particles and Saffil® alumina short fibres. This allows for the calculation of phase stresses and thus the load partitioning. The mean elastic misfit stresses were calculated using an Eshelby type modelling. Considering the external load, prediction of the phase-specific stresses for elastic composite deformation was performed and the results were compared to the experimental data obtained. Matrix elastic lattice strains reveal high plastic anisotropy due to the activation of different deformation modes in the form of crystallographic slip and mechanical twinning. The formation of twins, verified by diffraction intensity shifts due to crystallographic reorientation, was found to affect the sharing of load between the participating phases. Consequently different regimes of composite deformation were specified. This comprises elastic regions characterized by linear strain and stress growth for all phases as well as plastic regions showing nonlinear distributions.