Displacement Rate and Temperature Effects in Fracture of a Hot‐Pressed Silicon Nitride at 1100° to 1325°C

Abstract

An MgO‐fluxed hot‐pressed silicon nitride was fractured in four‐point flexure between 1100° and 1325°C at three crosshead speeds. Above 1200°C, a temperature and strain‐rate dependence of fracture stress and KIc was seen. Scanning and transmission electron microscopy were used to analyze as received and fractured material. A map of temperature vs crosshead speed was drawn showing regions where subcritical cracking was or was not observed and a transition region where microcracks and voids were detected.