Evolution of Microstructure and Intergranular Glass Chemistry in Plastically Deformed Nanocrystalline Si3N4 Ceramics. Issue 1 (30th September 2014)

• Record Type: Journal Article
• Authors: Wananuruksawong, Raayaa; Shinoda, Yutaka; Akatsu, Takashi; Wakai, Fumihiro; Rouxel, T.
• Is Part Of: Journal of the American Ceramic Society. Volume 98:Issue 1(2015)
• Page Start: 178
• Page End: 185
• Publication Date: 2014-09-30
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.13259
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace13259-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Nanograined Si₃N₄ ceramics with Y₂O₃–Al₂O₃–MgO as sintering additive exhibited superplastic elongation of &gt;300% at 1923 K with an initial strain rate of 5 × 10⁻⁴ s⁻¹. Flow stress was less than 4 MPa up to elongation of 130%. In the later stage of deformation, the flow stress increased with strain due to the grain growth and the alignment of elongated grains. The volume fraction of glassy phase significantly reduced due to vaporization of glassy phase. The chemical analysis by TEM/EDS revealed that the chemical composition of the near Si₃N₄ grain surface was different from that of the interior of the glass pocket at multigrain junctions due to absorption of additive cations on the Si₃N₄ grain. The chemistry of intergranular glassy phase changed significantly in the later stage of deformation accompanying the microstructural evolution. It is suggested that the flow stress, which depends on the viscosity of intergranular glassy phase, varies with the change in glass chemistry during deformation.</p> </abstract>