CREEP AND STRESS RUPTURE BEHAVIOR OF AN ADVANCED SILICON-NITRIDE .2. CREEP RATE BEHAVIOR

In Part I of this paper, experimental observations on creep testing of 74 tensile specimens of an advanced silicon nitride were presented. I n this part, equations are developed for predicting creep rates in the primary and secondary regimes in the temperature range 1477-1673 K. T he resulting model predicts creep strain rates to within a factor of t wo. The underlying phenomenological basis, which employs an activation energy approach, is discussed. The mechanisms that are likely to be r esponsible for the transiency of the primary creep regime and for the unique stress and temperature dependencies of the creep rates are expl ored.