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Titanium’s high-temperature elastic constants through the hcp–bcc phase transformation

2004; Elsevier BV; Volume: 52; Issue: 7 Linguagem: Inglês

10.1016/j.actamat.2004.01.002

1873-2453

Hirotsugu Ogi, Satoshi Kai, Hassel Ledbetter, Ryuichi Tarumi, Masahiko Hirao, Kazuki Takashima,

Microstructure and mechanical properties

The five independent elastic constants of hexagonal monocrystal titanium were determined up to the phase-transformation temperature, and the two isotropic elastic constants of polycrystalline titanium were determined beyond, up to 1300 K. Anomalous temperature dependences were observed just below the phase-transformation temperature: C11 and C66 increase with increasing temperature whereas C33 and C44 remarkably decrease, for example. To determine the Cij, we used the free-vibration resonance frequencies obtained by electromagnetic acoustic resonance. After the phase transformation, the resonance frequencies changed little with the temperature increase, showing that the bcc-phase elastic constants change little with temperature. The polycrystalline elastic constants remained unchanged up to 1300 K after the phase transformation. The anomalous temperature dependence near the transformation is interpreted in terms of the small c/a ratio of the hcp phase and change of the atomic distances to meet the Burgers lattice relationship. Temperature-insensitive elastic constants in the bcc phase suggest the stabilizing of the bcc phase with increasing temperature.