Study of the effect of cooling/heating rate on the thermal properties of ni-ti alloy (SMA) after annealing at different parameters

The research focused on evaluating the effect of different scanning calorimetric (DSC) rates of the cooling/heating process on changes in the phase transformation parameters of Ni-Ti shape memory alloy (SMA) after its prior annealing at different temperatures. The material used in the study was a spring SMA actuator, from which samples were taken for DSC testing. Initial study included the identification of the chemical composition of the material. All phase transformation temperatures were estimated from DSC curves using the tangent intersection method, as a commonly accepted way. Following annealing at various selected temperatures, changes in the shapes of the calorimetric profiles recorded during heating and cooling of the material were obtained. It is therefore clear that annealing promotes modification of the SMA microstructure. It was shown that, in general, there is an influence of the cooling/heating rate performed in the DSC on the evaluated thermal characteristics of the tested material. This influence is perhaps not so pronounced if one takes the states of the material after annealing conducted at different temperatures. With regard to the individual anneals, some of the characteristic transformation temperatures were sensitive to changes in cooling/heating rates, while in others this effect was not likely to be observed.