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Some Remarks on the fcc-fct Phase Transformation in InTl Alloys
DMMMSA - University of Padova, via Trieste 63, 35121 Padova,
Italy
* To whom correspondence should be addressed.
Zimmer and collaborators have recently proposed an alternative approach to Landau's for phase transformations, in which they replace the energy expression in terms of polynomials, a stiff family of functions, with one in terms of more f lexible functions, for instance certain splines. One of the arguments in favor of this more f lexible choice is the inability of an energy proposed earlier by Ericksen and James to f it reasonably well all the elasticities of an InTl alloy, in particular the wide difference in the measured \hat{L}44 and \hat{L}66 elasticities of the InTl martensite. While the proposal of Zimmer is theoretically very interesting and f it for numerical applications, and shows potential for modelling materials with complex internal structure, here I show that the pessimism about the standard Landau approach is indeed excessive as far as the weak points of the Ericksen-James energy are concerned. I propose a fourth-degree polynomial energy which extends the one of Ericksen and provides a fairly accurate f it of the equilibria as well as the elasticities for an In15.5\%Tl alloy; and perhaps also for different compositions in the InTl family. The starting point is the version of Ericksen's theory [5] given in [12]. Key Words: Nonlinear thermoelastic crystalline solids, elastic moduli, stability and bifurcation, phase transformations in the solid state, Landau theory, shape memory alloys, Indium-Thallium alloys.
First published on March 11, 2009, doi:10.1177/1081286509102513 |
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