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Micromechanics of Transformation Superplasticity in Ti-6Al-4V/TiB(w) Composites.

DE200415006873

Publication Date	2001
Personal Author	Schuh, C.; Dunand, D. C.
Page Count	16
Abstract	Transformation superplasticity is a deformation mechanism induced by thermally-cycling a polymorphic material through the phase transformation range while simultaneously applying an external biasing stress. Unlike microstructural superplasticity, which requires a fine, equiaxed grain structure, this mechanism can be applied to coarse-grained alloys and composites. In this article, we review our research on transformation superplasticity of Ti-6Al-4V/TiB-whisker reinforced composites, during thermal cycling through the titanium(alpha)/(beta) transformation range. The composites exhibit Newtonian flow and superplastic extension under these conditions. We describe the constitutive behavior of composites containing 0, 5 and 10 vol% reinforcing whiskers, and consider the effects of load transfer from matrix to whisker on superplastic deformation using existing rheological models. Additionally, strain hardening due to gradual whisker alignment is observed, and rationalized in terms of increased load transfer for aligned whiskers.
Keywords	Composites Micromechanics Transformation superplasticity Alignment Deformation Phase transformation Strain hardening Thermal cycling Titanium Transformations Alloys Thermally-cycling Polymorphic materials Phase transformation range External biasing stress
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200418

Micromechanics of Transformation Superplasticity in Ti-6Al-4V/TiB(w) Composites.

Micromechanics of Transformation Superplasticity in Ti-6Al-4V/TiB(w) Composites.
DE200415006873

Publication Date	2001
Personal Author	Schuh, C.; Dunand, D. C.
Page Count	16
Abstract	Transformation superplasticity is a deformation mechanism induced by thermally-cycling a polymorphic material through the phase transformation range while simultaneously applying an external biasing stress. Unlike microstructural superplasticity, which requires a fine, equiaxed grain structure, this mechanism can be applied to coarse-grained alloys and composites. In this article, we review our research on transformation superplasticity of Ti-6Al-4V/TiB-whisker reinforced composites, during thermal cycling through the titanium(alpha)/(beta) transformation range. The composites exhibit Newtonian flow and superplastic extension under these conditions. We describe the constitutive behavior of composites containing 0, 5 and 10 vol% reinforcing whiskers, and consider the effects of load transfer from matrix to whisker on superplastic deformation using existing rheological models. Additionally, strain hardening due to gradual whisker alignment is observed, and rationalized in terms of increased load transfer for aligned whiskers.
Keywords	Composites Micromechanics Transformation superplasticity Alignment Deformation Phase transformation Strain hardening Thermal cycling Titanium Transformations Alloys Thermally-cycling Polymorphic materials Phase transformation range External biasing stress
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200418