Quantifying nanoscale 3D stresses in zirconium and hydrides

Zirconium alloys are widely used to manufacture the core components of nuclear reactors. Despite having good mechanical properties, they are susceptible to hydrogen embrittlement and hydride formation. In this study, scanning three-dimensional synchrotron X-ray diffraction is employed to determine, for the first time, the 3D internal stresses within hydrides and the surrounding zirconium matrix at 200 nm spatial resolution. The three-dimensional measured grain morphologies are imported into a crystal plasticity finite element model to simulate the evolution of localized stresses induced by hydride precipitation. Both experimental and numerical results consistently reveal significant compressive hydrostatic stresses within hydrides, with magnitudes exceeding 1 GPa, accompanied by pronounced variations in the individual stress components. Stresses and dislocation densities are localized at the hydride-zirconium boundaries. A force equilibrium analysis demonstrates that the measured stresses in the surrounding zirconium matrix are sufficient to recover internal stresses within hydrides, further validating the measured values. Combining high resolution 3D X-ray diffraction with crystal plasticity modeling, this manuscript highlights the micromechanics of transformation-induced stress/strain in hydride-zirconium boundaries.