Computation of Effective Steady‐State Creep of Porous Ni–YSZ Composites with Reconstructed Microstructures

Abstract

This paper investigates the effective steady‐state creep response of porous Ni–YSZ composites used in solid oxide fuel cell applications by numerical homogenization based on three‐dimensional microstructural reconstructions and steady‐state creep properties of the constituent phases. The Ni phase is found to carry insignificant stress in the composite and has a negligible role in the effective creep behavior. Thus, when determining effective creep, porous Ni–YSZ composites can be regarded as porous YSZ in which the Ni phase is counted as additional porosity. The stress exponents of porous YSZ are the same as that of dense YSZ, but the effective creep rate increases by a factor of 8–10 due to porosity. The relationship of creep rate and volume fraction of YSZ computed by numerical homogenization is underestimated by most existing analytical models. The Ramakrishnan–Arunchalam creep model provides the closest approximation among all analytical models.