SZURMAN Ivo VSB-Technical University of Ostrava

Spoluautoři KURSA Miroslav, KOCH Daniel

For production of Ti-Ni based alloys mostly the cleanest raw materials are used. The typical input materials for preparing the alloys are titanium sponge (pure titanium rods) and metallic nickel (pellets, electrolytic piece, etc.). Nickel has usually lower contents of interstitial impurities. The titanium sponge may on the other hand contain up to 400 - 800 ppm of oxygen and approx. 25 - 80 ppm of carbon. The current key technologies for preparation of alloys of the Ni-Ti-(Me) system are most often realized in a vacuum. Several methods are used here (melting by electron beam – EMB, vacuum arc melting – VAR, high-frequency induction vacuum melting in graphite crucibles – VIM). Plasma melting represents another possible technology. The properties of these alloys (both shape memory and mechanical) are significantly affected by the contents of these elements, similarly to other materials. The degradation of properties is also affected by the quality of the surface and the presence of hydrogen. This article deals with examination of possibilities of recycling of Ti-Ni alloys using older alloys prepared and used before. The differences between the newly prepared alloys (from raw materials) and the alloys recycled with respect to the contents of gas and other impurities are also discussed. Microstructures were evaluated by OM and SEM techniques. Vacuum induction furnace with graphite crucible was used for melting followed by centrifugal casting into rods with diameter of 20 mm and length of 225 mm.