Theoretical and experimental fundamental research of shape memory alloys dilatation in the temperature range of stress-free forward and reverse martensitic transformations.

Abstract: Three kind of shape memory-alloys (SMA?s) - single crystals Cu-Al-X (X=Zn, Mn, Ni), and MnCu as well as TiNi-polycristals - are investigated dilatometrically in the temperature interval of martensitic transformations.

Mechanisms of the dilatation effects in shape memory alloys are analyzed. On that basis is an accommodation degree introduced. Its values were calculated for all investigated SMA-samples: they lie in an interval from 75% up to 99%.

Interrelation between thermal expansion of SMA's and their physical (elasticity modulus), thermodynamical (entropy) and crystallographical (shear systems) characteristics is treated theoretically and discussed.

The width extension of the thermal hysteresis loops depending on the scanning rate is also investigated dilatometrically, and a physical limiting of the work-frequency of SMA-actuators is proved and discussed.