Dependence of the third-order coefficients in Landau free energies for bcc{r_arrow}fcc structural transition on hydrogen concentration in zirconium hydrides
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611 (Japan)
Young{close_quote}s modulus E and the modulus of rigidity G of zirconium hydrides ZrH{sub x}(0.9{le}x{le}1.65) at 941 and 1001 K have been obtained as a function of hydrogen concentration c by measuring resonance frequencies for bending and torsion vibrations of a polycrystalline wire. As c increases, observed E and G increase in the bcc {beta} phase, slightly increase linearly in the {beta}+{delta} phase, and then decrease in the fcc {delta} phase. On the basis of a phenomenological free energy in terms of strain components taking account of space group symmetry, two types of Landau expansion of the free energies for the {beta} phase in terms of the strain components which play an important role in the structural phase transition between the {beta} and the {delta} phases are examined. The observed E and G are assumed to be the same as the second-order coefficients of the free energy for the Bain distortions, which occur at the structural phase transition. The dependence of the third-order coefficients on c permits the expanded free energies to describe the fact that the {beta} phase is more stable than the {delta} phase at low c. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 526864
- Journal Information:
- Journal of Applied Physics, Vol. 82, Issue 3; Other Information: PBD: Aug 1997
- Country of Publication:
- United States
- Language:
- English
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