首页|A simple method to improve superplastic elongation and strength of 3Y-TZP deformed at high strain-rates

A simple method to improve superplastic elongation and strength of 3Y-TZP deformed at high strain-rates

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  • NETL
  • NSTL
  • Trans Tech Publications Ltd
During superplastic deformation (SPD) of tetragonal zirconia polycrystals containing 3 mol% yttria (3Y-TZP) at high strain-rates, a number of crack-like flat cavities having very narrow gaps lying along grain boundaries mostly normal to the tensile axis are produced in addition to conventional cavities. The formation and growth of these flat cavities are responsible for the strain softening that appears on the true stress versus true strain curves. The growth and coalescence of the flat cavities were a main cause of the degradation of elongation to fracture. We have found that a simple treatment, in which the superplastic deformation is temporally stopped, i.e., the cross-head movement is reversed and accordingly the applied load is removed, and then the specimen is kept at the test temperature for several minutes, is surprisingly effective to reduce the flat cavities. Carrying out this simple treatment repeatedly, after 30% nominal stain during the SPD, led to an increace in total elongation by about three times larger than that of a specimen not subjected to such a treatment. This treatment can also recover the strength and accordingly mechanical properties of the superplastically deformed 3 Y-TZP to that of the undeformed state. This finding is believed to be quite significant for practical applications of superplasticity in 3Y-TZP, because the flat cavities can be closed very simply by keeping a product at the forming temperature after or during the superplastic forming process.

superplasticityY-TZPconstant strain-ratestress-strain curvecavitationflat cavities

Yoshinobu Motohashi、Makoto Kikuchi、Takaaki Sakuma、Eitaro Yukutake、Isao Kuboki

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Research Center for Superplasticity, Ibaraki University, Hitachi, Ibaraki, 316-8511, Japan

Graduate student of Ibaraki University, at present, Hitachi High Tech Co

Ibaraki Prefectural Industrial Technology Center, Ibarakimachi, Ibaraki, 311-3195, Japan

Kogakuin University, Hachiouji, Tokyo, 192-0015, Japan

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2010

10.4028/www.scientific.net/KEM.433.339

Key engineering materials

Key engineering materials

ISSN：1013-9826
年,卷(期)：2010.433
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