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Tensile fracture during transformation superplasticity of Ti–6Al–4V

Published online by Cambridge University Press:  26 November 2012

C. Schuh
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive, Room 2036, Evanston, Illinois 60208
D. C. Dunand
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive, Room 2036, Evanston, Illinois 60208
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Abstract

During thermal cycling through the α–β phase transformation under the action of a small external biasing stress, Ti alloys exhibit an average deformation stress exponent of unity and achieve superplastic strains. We report tensile experiments on Ti–6Al–4V with an applied stress of 4.5 MPa, aimed at understanding the failure processes during transformation superplasticity. The development of cavities was assessed as a function of superplastic elongation, and macroscopic neck formation was quantified at several levels of elongation by digital imaging techniques. The effects of thermal inhomogeneity on neck initiation and propagation were also elucidated experimentally. Tensile ductility during transformation superplasticity is compared with that during isothermal creep at the average, effective cycling temperature, and a numerical model is used to show the effect of thermal gradients in limiting superplastic elongation.

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Articles
Copyright
Copyright © Materials Research Society 2001

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