Creep and failure at metal-oxide interfaces

Small-scale bicrystal creep experiments were performed on contacts formed via in situ high-temperature diffusion bonding of metal-oxide interfaces including Ag-ZrO₂, Pd-ZrO₂, Pt-ZrO₂, and Ag-high entropy oxide_. This work characterizes deformation and failure at metal-oxide interfaces during mechanical loading. Interfacial sliding can be activated easily, while tensile interfacial creep was not observed at any condition of stress or temperature measured. Plastic strain, instead, localizes within the metal under tensile loading. A variety of mechanisms for plastic strain occur in the metal including lattice dislocation-mediated plasticity, twinning, low-angle grain boundary formation, and low-angle grain boundary creep. Surface and low-angle grain boundary diffusion occur under conditions where no metal-oxide tensile creep is observed, highlighting the significant differences in their interfacial mechanical response. High-temperature interfacial failure occurs when the mean curvature at the contact neck is approximately zero and the applied stresses comparable to brittle fracture stresses. The brittle fracture stresses were measured to be ${\sigma }_f=180\pm 90MPa$ at the Ag-ZrO₂ interface at $225{}^{\circ }C$, ${\sigma }_f=460\pm 160MPa$ at the Pd-ZrO₂ interface at $680{}^{\circ }C$, and ${\sigma }_f=640\pm 440MPa$ at the Pt-ZrO₂ interface at $1010{}^{\circ }C$.