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The Mechanism of Mixed-Mode Phase Transformations

Published online by Cambridge University Press:  10 February 2011

R. C. Pond ,
P. Shang ,
T. T. Cheng  and
M. Aindow
R. C. Pond
Affiliation:
Materials Science and Engineering, University of Liverpool, Liverpool, L69 3GH, UK.
P. Shang
Affiliation:
Dept. of Materials, University of Oxford, Oxford, OXI 3PH, UK
T. T. Cheng
Affiliation:
IRC in Materials, University of Birmingham, Birmingham, B15 2TI, UK.
M. Aindow
Affiliation:
Dept. of Metallurgy and Materials Eng., University of Connecticut, Storrs, CT 06269, USA.
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Abstract

The topological theory of interfacial defects and the associated flux analysis are reviewed. It is shown that the shears and diffusive fluxes associated with the motion of disconnections can be determined directly from their crystallographic characteristics, and that the effects of changes in chemical composition, interfacial misfit and ordering can be incorporated into the analysis. The special conditions are identified for which there is conservation of atomic sites during the motion of disconnections. It is shown that, under these circumstances, disconnection motion may result in mixed-mode displacive-diffusive transformations whereby diffusion is required for the transformation to proceed but the interfaces exhibit crystallographic characteristics which one would normally associate with a martensitic transformation. It is shown that the growth of γ lamellae in TiAl-based alloys is an example of such a mixed-mode transformation.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 586: Symposium M – Interfacial Engineering for Optimized Properties II , 1999 , 21
Copyright
Copyright © Materials Research Society 2000

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References

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