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Nucleation of the α / γ Massive Phase Transformation in Titanium- 48at% Aluminum

Published online by Cambridge University Press:  02 July 2020

J.E. Wittig  and
W.H. Hofmeister
J.E. Wittig
Affiliation:
Materials Science and Engineering, Vanderbilt University, Box 1683 Station B, Nashville, TN, 37235
W.H. Hofmeister
Affiliation:
Materials Science and Engineering, Vanderbilt University, Box 1683 Station B, Nashville, TN, 37235
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Massive phase transformations exhibit a change in crystal structure without a change in composition. Nucleation and growth of this difTUsionless transformation has been studied in numerous systems including Cu-Zn, Ag-Zn and Ag-Al. There is general agreement that heterogeneous grain boundary nucleation occurs with a rational orientation relationship with at least one of the parent grains, although growth of the massive product can often occur with a partially coherent interface.

The typical Ti-48at%Al microstructure is a lamellar structure of hexagonal α2 (DO19 superlattice) and the ordered tetragonal γ phase (Ll0 with c/a = 1.01). Water or ice brine quenching of the high temperature disordered α phase results in a partial massive transformation of a into γ. Electron beam melting has been used to further suppress the equilibrium transformations. However, the current study uses rapid solidification by electromagnetic levitation and twin anvil splat quenching (cooling rates > 106 K/s) to capture earlier stages of the transformation.

Type
Metals and Alloys
Information
Microscopy and Microanalysis , Volume 4 , Issue S2: Proceedings: Microscopy & Microanalysis '98, Microscopy Society of America 56th Annual Meeting, Microbeam Analysis Society 32nd Annual Meeting, Atlanta, Georgia July 12-16, 1998 , July 1998 , pp. 538 - 539
Copyright
Copyright © Microscopy Society of America

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References

References:

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