Interface Homogenization Approach for Mechanical Healing Driven by Pressure Solution

Pressure solution involves mass transfer by dissolution, diffusion, and precipitation in pores or at grain interfaces, which may result in mechanical healing. Dislocation glide is another deformation mechanism that plays a significant role in the behavior of polycrystals. In this paper, we use Eshelby's self-consistent homogenization scheme with imperfect interfaces to calculate the macroscopic mechanical and diffusive properties of an elasto-viscoplastic porous composite made of imperfectly bonded crystals. Using halite as a model material, the proposed self-consistent model is calibrated and verified against published results of experimental creep tests. Simulations highlight that healing by grain boundary precipitation (by contrast with in-pore precipitation) is a limiting factor for pressure solution, because healed interfaces have lower diffusivity than fluid-filled interfaces. The homogenization approach provides an explanatory framework for the lower creep deformation observed for larger grains, and forecasts lower diffusivity for smaller grains. Sensitivity analyses show that grain boundary healing decelerates specimen compaction, while precipitation in the pores controls the evolution of effective diffusivity.