Influence of holding between the thermal cycles on recovery in martensitic transformation temperatures in TiNi alloy

摘要

The aim of the present work was to study the features of the recovery of properties of the TiNi alloy during isothermal holding after thermal cycling in the temperature range of 200?÷?0°C.?It was found that if the holding temperature was less than 200°C, then the martensitic transformation temperatures additionally decreased in the thermal cycle after holding. If the holding temperature was equal to 200°C, then no variation of martensitic transformation temperatures was found. If the holding temperature was higher than 200°C, then the transformation temperatures increased in the thermal cycle after holding, hence the recovery of the properties of the alloy was observed. The higher the holding temperature, the more intensive the recovery in transformation temperatures. Since the variation in the martensitic transformation temperatures is caused by a change in the defect density, then it can be assumed that holding of the alloy at a temperature that is higher than the maximum thermal cycling temperature (200°C) results in the redistribution or annihilation of dislocation structures in the alloy and this is the nature of the recovery of the martensitic transformation temperature. Thus, intermediate isothermal holding of the TiNi?alloy at temperatures higher than the maximum temperature in thermal cycle allows restoring the parameters of martensitic transformations that were varied by previous thermal cycling.