Direct measurement of residual stresses and their effects on the microstructure and mechanical properties of heat-treated Si₃N₄ ceramics

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• 作者：Gangfeng Guo ; Jianbao Li ; Xiaozhan Yang ; Hong Lin ; Long Liang ; Mingsheng He ; Xuguang Tong and Jun Yang
• 关键词：Residual stresses ; Crystallization ; Microstructure ; Mechanical properties ; Silicon nitride
• 刊名：Acta Materialia
• 出版年：2006
• 出版时间：May 2006
• 年：2006
• 卷：54
• 期：9
• 页码：2311-2316
• 全文大小：266 K

文摘

For the first time, the residual stresses induced during crystallization of the amorphous grain boundary phase in heat-treated Si₃N₄ with Yb₂O₃ as a single additive have been directly measured by X-ray residual stress analyses. The magnitude of the room-temperature strength reduction is comparable to that of the corresponding residual stress. Most of the large residual stress is introduced by large volume changes during the phase transformation. Microscopically, the large residual stress essentially results in the formation of flaws including strain contrast and transgranular cracks in elongated β-Si₃N₄ grains. Consequently, the large residual stress is a controlling factor for the reduction of the room-temperature strength in the heat-treated material. However, the influence of residual stresses on mechanical properties would be less at higher temperatures.