Pretransformation twinning in In-Tl alloys

Abstract

The mechanical-response coefficients controlling the torsional vibrations of In-Tl alloy bars oriented along the [100] and [110] directions have been measured as a function of temperature at resonance frequencies of about 100 Hz. Both coefficients have been observed to decrease almost linearly at the same rate as the temperature approaches the martensitic-transformation temperature. It is proposed that this unusual low-frequency premartensitic shear behavior represents dynamic and reversible twinning on a very fine scale.