CONTRIBUTION TO STRUCTURAL AND METALLURGI CAL CHARACTERISTICS OF TINISHAPE-MEMORY MATERIALS

Structural and metallurgical characteristics of the three types of TiN i shape memory alloys (A-Ti-49.5 at.% Ni, B-Ti-49.2 at.% Ni, C-Ti-41.7 at.% Ni-8 at.% Cu) for medical applications were investigated and com pared in presented paper. To achieve information of structural propert ies of these alloys, the light microscopy, TEM, WDA, EDAX, and X-ray a nalysis were used. The transformation temperatures of investigated mat erials were determined by use of the resistometric method. Tensile tes ts and microhardness measurements were performed. The presence of Ti2N i (Ti4Ni2(O,N)(x)) particles and carbide, nitride, and oxide or carbid enitride inclusions were detected in all the types of alloys. As it fo llows from the results, the initial structure of individual alloys con sisted of B2 and B19' phases but their volume fraction was different a t room temperature, depending on the previous treatment. The applied t reatment does not influence the determined crystallographical orientat ion relationships between B2 and B19' phases: As we have found, deform ation behaviour of the studied alloys was dependent on the position of the testing temperature with respect to the transformation temperatur es as well as on the work hardening intensity.