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Mechanism of Superplastic Flow in a Fine‐Grained Ceramic Containing Some Liquid Phase
Author(s) -
WANG J.G.,
RAJ R.
Publication year - 1984
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1984.tb19725.x
Subject(s) - materials science , ceramic , superplasticity , deformation (meteorology) , composite material , strain rate , compression (physics) , flow stress , grain size , deformation mechanism , microstructure , tension (geology) , phase (matter) , metallurgy , stress (linguistics) , mineralogy , geology , linguistics , chemistry , philosophy , organic chemistry
Several results pertaining to large deformations at fast strain rates in a fine‐grained ceramic material are described. Results for strain‐rate, grain size, and temperature dependence of the flow stress are presented. They show that (a) ultrafine‐grained ceramics are capable of high rates of deformation (about 10 −4 to 10 −4 s −1 ) at quite low stresses (1 to 20 MPa); (b) the mechanism of deformation is the enhanced rate of matter transport through the liquid phase segregated in the grain boundaries; (c) either uniaxial compression or tension tests may be used to determine the flow properties, except that a correction must be implemented for friction in the case of compression tests; and (d) microstructural changes can occur during deformation which influence the flow behavior. The ceramic is almost infinitely ductile in compression, whereas in tension elongations as large as W5% in one material, and more than 400% in another, were obtained. A model material, β‐spodumene glass‐ceramic, was used for this study but the results are likely to hold for other materials with equivalent microstructures, e.g., liquid‐phase‐sintered or hot‐pressed materials such as the nitrogen ceramics