Characteristics of porous nickel-titanium alloys for medical applications.

We investigate the behavior of NiTi porous alloys, possessing the property of shape memory, by using different characterization methods XPS, Auger, DSC and SEM. The study mainly focuses on the determination of porosity, surface characteristics and the phase transformation. In the case of porous material the biomechanical compatibility is closely related to the internal structure and porosity distribution. To describe appropriately the influence of the properties of NiTi on the memory shape, two types of materials provided by different sources has been analyzed. Despite the fact that both materials present different pores size, they exhibit an open and interconnected porosity. Our measurements show that the temperature of the inception of the martensite-austenite phase transition occurs at 60 degrees C, which is by 20 degrees C greater than the body temperature. Moreover, we show that the surface characteristics can be greatly influenced by heat treatment. Furthermore, we observe that the R-phase occurs only for one of the used materials after its heat treatment. The correlation between the composition and the other characteristics measured has been found.