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Superplastic Foaming of Titanium and Ti-6Al-4V

Published online by Cambridge University Press:  10 February 2011

D. C. Dunand  and
J. Teisen
D. C. Dunand
Affiliation:
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA, dunand@nwu.edu.
J. Teisen
Affiliation:
Department of Materials, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland.
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Abstract

Solid-state foaming of metals can be achieved by hot-isostatic pressing of powders in presence of argon followed by expansion of the resulting high-pressure argon bubbles at ambient pressure and elevated temperature. This foaming technique was first demonstrated by Kearns et al. [1] for Ti-6Al-4V, but is limited by its low creep rate and ductility, which lead to early cell wall fracture. We address these issues by performing the foaming step under superplastic conditions. Rather than using microstructural superplasticity (requiring fine grains which are difficult to achieve in porous powder-metallurgy materials), we used transformation superplasticity, which occurs at all grain sizes by biasing with a deviatoric stress (from the pore pressure) of internal stresses (from the allotropic mismatch during thermal cycling about the allotropic temperature range). As compared to control experiments performed under isothermal creep conditions, superplastic foaming under temperature cycling of unalloyed titanium and alloyed Ti-6Al-4V led to a significantly higher pore volume fraction and higher foaming rate.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 521: Symposium R – Porous & Cellular Materials for Structural Applications , 1998 , 231
Copyright
Copyright © Materials Research Society 1998

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References

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