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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.44  No.2 (2003)  >  pp.226-231

MATERIALS TRANSACTIONS
<<Previous article Vol.44  No.2 (2003)   pp.226 - 231 Next article>>

Compressive Deformation of Partially Crystallized Amorphous Si-B-C-N Ceramics at Elevated Temperatures

Satoru Ishihara1), Tsukasa Hirayama1), Joachim Bill2), Fritz Aldinger2) and Fumihiro Wakai3)
1) Ceramics Superplasticity Project, ICORP, Japan Science and Technology Corporation
2) Max-Planck-Institut für Metallforschung, Pulvermetallurgisches Laboratorium, Stüttgart
3) Tokyo Institute of Technology, Materials and Structures Laboratory


The deformation behavior of Si–B–C–N ceramics derived from a polymer precursor has been investigated by compression tests at high temperatures. The hot isostatic pressing of pyrolyzed powder compact was conducted at 1450°C and at 900 MPa in order to obtain a dense ceramic monolith. The material consisted of the amorphous matrix and the dispersed Si3N4 particles with the diameter of about 20 nm. While only apparent elastic deformation was observed at the testing temperatures up to 1500°C, significant plastic deformation occurred at temperatures higher than 1650°C. The plastic deformation is considered to be caused by the viscous flow of the amorphous matrix. The flow stress at the testing temperatures in the range of 1650 to 1750°C increased with initial strain rate. The flow stress was not proportional to the strain rate. The shear viscosity at 0.02 strain was about 1011–1013 Pa s and decreased proportionally to about −0.75 power of the strain rate. The decrease in shear viscosity is considered to show a strain localization behavior. Strain hardening was observed during the plastic deformation. As the reason of the strain hardening, the crystallization can be considered, in addition to the decrease in atomic site defects during the deformation.


Keyword:
precursor-derived ceramics, bulk, amorphous, hot isostatic pressing, non-Newtonian viscous flow

Received: September 19, 2002
Accepted: December 02, 2002 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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