Metastable effects on martensitic transformation in SMA (I) recoverable effects by the action of thermodynamic forces in parent phase

Summary The applicability of SMA requires a matching of the properties with the technological needs. The metastability effects and the phase coexistence can produce, via atomic diffusion, some changes in the expected properties against time. The careful analysis of the external thermodynamic forces (stress) on the parent phase of a Cu-Al-Zn single crystal alloy establishes a proportional minor change in critical transformation stress (near 1 per cent of the external stress). Via the Clausius-Clapeyron coefficient, the stress effects show a similar behaviour but faster than the room temperature effects on the transformation temperature M_S. In parent phase, the effect of the thermodynamic force regarded as an M_S shift lies between 10 to 15 percent of temperature change.