Modeling hydrogen solvus in zirconium solution by the mesoscale phase-field modeling code Hyrax

A phase-field modeling code with Calphad-based free energy functions, Hyrax, has been used to model the hydrogen solvus in alpha-zirconium solution and the formation of the zirconium-hydride phase in the zirconium matrix. The modeled hydrogen solvus was compared against published experimental data; this is considered the first direct validation of Hyrax output. The effect of external stress on hydrogen solvus and hydride formation has also been modeled. A tensile stress was uniformly applied to a single zirconium crystal and a bi-crystal system. We observed that the stress does not affect hydrogen solvus but does cause hydride to accumulate in the crystalline which has the c-axis parallel to the stress direction.52