Title: Creep mechanism and microstructure evolution in silicon nitride ceramics

Authors: F. Lofaj

Addresses: Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, 043 53 Kosice, Slovakia

Abstract: Tensile creep processes in a commercial grade of silicon nitride, SN 88, are reviewed with the focus on cavitation and microstructure changes. Experimental measurements showed that cavitation at multigrain junctions is the rate controlling creep mechanism. The cavitation creep model of Luecke and Wiederhorn was extended to explain non-power law behaviour and strong creep asymmetry. Secondary phase composition changes after prolonged creep tests resulted in the formation of Yb-disilicate phase at the expense of Yb-oxynitride due to oxidation. Such secondary phase changes affect residual glass composition, which has crucial effect on the processes involved in cavitation and resulting creep behaviour.

Keywords: silicon nitride; tensile creep; cavitation; dilatation stresses; grain boundary sliding; GBS; viscous flow; solution-precipitation; crystalline secondary phases; residual glass; creep mechanisms; microstructure; ceramics.

DOI: 10.1504/IJMPT.2007.013091

International Journal of Materials and Product Technology, 2007 Vol.28 No.3/4, pp.487 - 513

Available online: 07 Apr 2007 *

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