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Quantitative analysis of microstructures produced by creep of Ti–48Al–2Cr–2Nb–1B: Thermal and athermal mechanisms

Published online by Cambridge University Press:  31 January 2011

M. A. Morris  and
M. Leboeuf
M. A. Morris
Affiliation:
Institute of Structural Metallurgy, University of Neuchêtel, Av. Bellevaux, 51, 2000 Neuchêtel, Switzerland
M. Leboeuf
Affiliation:
Institute of Structural Metallurgy, University of Neuchêtel, Av. Bellevaux, 51, 2000 Neuchêtel, Switzerland
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Abstract

A γ-based TiAl alloy with equiaxed microstructure and fine grain size has been studied to analyze the deformation mechanisms responsible for the creep behavior. The microstructures produced by creep and high temperature deformation have been examined by TEM to obtain information about the different aspects characterizing the primary and secondary stages of creep. Mechanical twinning has been confirmed to occur in a fraction of the grains that never exceeds 50% while 1/2 ‹110› dislocations are active within all the γ grains. The twins are only responsible for a small amount of strain, but they lead to a subdivision of the microstructure and determine (directly or indirectly) the hardening process observed during the primary stage of creep. We have proposed that during the secondary stage the creep rate is determined by the unblocking of pinned dislocations by processes such as a pipe diffusion or cross slip that allow thermally activated glide of 1/2‹110› dislocations on (001) planes.

Type
Articles
Information
Journal of Materials Research , Volume 13 , Issue 3 , March 1998 , pp. 625 - 639
Copyright
Copyright © Materials Research Society 1998

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