Abstract

We studied the processes of structure evolution and phase formation in the material during hot-pressing of ultrafine (highly dispersed) composite powders of the [Si3N4-10% Y2O3] system. Densification of the powder occurs under the conditions facilitating chemical interaction in the complex heterogeneous system. The sintering mechanism of UFCP consists of a stage of self-activated rapid grain growth in the solid phase mainly in the 1120–1150°C range and a stage of liquid phase sintering in the 1150–1650°C range under the conditions of varying composition, viscosity, and content of the liquid phase. It was established that densification is initiated by a low-melting yttrium silicate type liquid phase that disappears after participating in the process leading to the formation of a high-melting liquid phase having a composition close to that of yttrium-silicon oxynitrides. The revealed regularities in the behavior of UFCP during the process of hot-pressing offer the possibility of controlling the structure evolution in them purposefully in order to obtain the required set of properties. The results of our studies are being used for obtaining engineering components.

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