Improved creep resistance in anisotropic silicon nitride

Tensile creep behavior of silicon nitride with aligned rodlike grains (anis otropic, silicon nitride), fabricated by superplastic forging, was investig ated at elevated temperatures. Creep rate of the anisotropic silicon nitrid e was about I order of magnitude lower than that of the isotropic one (with out forging). The stress sensitivities for the isotropic and anisotropic sp ecimens at 1200 degreesC were 2.1 and 2.6, respectively, and that for the a nisotropic specimen at 1250 degreesC was 3.6. The grain alignment should ca use a remark-able improvement in the creep resistance when a tensile stress is applied along the alignment direction.