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Hot extrusion of nanocrystalline yttria-stabilized tetragonal zirconia polycrystals

Published online by Cambridge University Press:  25 October 2016

Tatsuo Kumagai
Tatsuo Kumagai*
Affiliation:
Department of Mechanical Engineering, School of Systems Engineering, National Defense Academy, Yokosuka-shi, Kanagawa 239-8686, Japan
*
a) Address all correspondence to this author. e-mail: kumagai@nda.ac.jp
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Abstract

Hot indirect extrusion behaviors of fully dense 3 mol% Y2O3-stabilized ZrO2 polycrystals with a grain size of 80 nm were investigated by using a conical graphite die. During early extrusion at 1843 K and a constant compression stress of 60–80 MPa, the relative moving billet velocity (v 0) shows a sharp maximum, followed by a continuous decrease until it reaches a steady-state v 0 value. Visual observations of the material flow by using graphite foil markers indicate that the deformation zone at the steady-state v 0 is well represented by a spherical velocity field. The decrease in v 0 corresponds to the transition from heterogeneous to homogeneous deformation. The stress exponent (n) of 2.07 was obtained from the log–log plots of the steady-state v 0 versus the external applied stress that is compensated by threshold and sliding friction stresses. This n value suggests plastic deformation through grain-boundary sliding in indirect extrusion.

Keywords

extrusionceramicstress/strain relationship

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Type
Articles
Information
Journal of Materials Research , Volume 31 , Issue 21 , 14 November 2016 , pp. 3290 - 3302
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Copyright
Copyright © Materials Research Society 2016 

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Footnotes

Contributing Editor: Yanchun Zhou

References

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