THE MARTENSITE STABILIZATION EFFECT IN TITANIUM NICKELIDE AFTER PRELIMINARY DEFORMATION BY COOLING UNDER STRESS IN AN INCOMPLETE TRANSFORMATION INTERVAL

When using thermosensitive sensors and servos, based on shape memory alloys (SMA), it is necessary to take into account the influence of shifting factors capable the temperatures of martensitic transformations (MP). One of these factors is the martensite stabilization effect (MSE), which manifests itself as an increase in reverse MP temperatures after preliminary deformation. Previous MSE studies allowed, based on experimental data, to hypothesize that this effect is due to damage to the boundaries orientation of the martensite domains. This suggests that minimizing or eliminating MSE is possible while minimizing damage to these boundaries. One of the ways to achieve this is to cool the SMA from the austenitic state under constant load in an incomplete temperature range of transformation. Numerical experiments performed within the framework of a microstructural model that takes into account MSE made it possible to determine the dependence of the temperature shift of the reverse transformation on the value of the fraction of direct transformation achieved during cooling. The results showed that the temperature shift remains zero or negligible until a certain critical fraction of the transformation is reached.