High‐Resolution Electron Microscopy Investigation of Viscous Flow Creep in a High‐Purity Silicon Nitride

The redistribution of intergranular amorphous films during creep deformation of Si 3 N 4 has been studied by high‐resolution transmission electron microscopy. The film thickness distribution of a high‐purity Si 3 N 4 material before and after creep was measured. A narrow range of film widths in the uncrept material and a bimodal distribution after creep were observed. These observations provided convincing evidence of the occurrence of viscous flow of intergranular amorphous films during creep deformation of Si 3 N 4 . Moreover, the creep response predicted by a viscous flow model was in good agreement with experimental data.