This proposal follows on from our successful experiment on ENGIN-X lin 2006, where we measured the development of strains in the aluminium and silicon phases of a common casting alloy, Al-7Si-0.4Mg. The experiment allowed us to evaluate the load transfer from the aluminium to the silicon, and to evaluate the strength of the silicon particles.However, data analysis is complicated because the particles fracture progressively during a tension test so the diffraction peaks contain data from both broken and intact particles. The proposed experiment will refine our estimates of the fracture strengths of the Si particles.We will identify the three elements of the particle stress due to mismatches between Si and Al of the thermal expansion coefficients, elastic moduli and plastic flow behaviour and, crucially, of the relaxation of the thermal stress as the Al yields.