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Quantitative Observations in Dislocation Mechanisms in Gamma TiAl

Published online by Cambridge University Press:  22 February 2011

B. Viguier,
M. Cieslar,
K. J. Hemker and
J. L. Martin
B. Viguier
Affiliation:
Institut Genie Atomique, EPFL, CH-1015 Lausanne, Switzerland
M. Cieslar
Affiliation:
Institut Genie Atomique, EPFL, CH-1015 Lausanne, Switzerland
K. J. Hemker
Affiliation:
Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD
J. L. Martin
Affiliation:
Institut Genie Atomique, EPFL, CH-1015 Lausanne, Switzerland
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Abstract

Quantitative TEM observations have been made on a series of gamma Ti47Al51Mn2 polycrystals that were deformed at different temperatures. Special attention has been given to determining the statistical variation of defect densities that occur at the different temperatures. The results, which are in good agreement with mechanical testing [J], indicate that three different mechanisms control deformation in this alloy: lattice friction and the formation of faulted dipoles at low temperatures, the pinning of ordinary dislocations at intermediate temperatures, and the bowing and looping of dislocations at high temperatures. The anomalous flow strength of this alloy has been found to be related to the intrinsic pinning of ordinary dislocations. Details of this pinning and subsequent unzipping process, which are the basis for the new local-pinning-unzipping (LPU) models[2-4], are outlined within.

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