Search

It is shown that the pressure treatment of titanium nickelide alloys should be carried out in two stages. At the first stage, ingots are deformed in order to transform the brittle cast structure, while at the second stage, the necessary shape is imparted to a semi-finished product along with the required structure and material properties. The deformability of TiNi alloy ingots largely depends on the content of impurities and the uniformity of a chemical composition, which is determined by the purity of a charge material and the smelting method. The deformability can be increased on the basis of using a titanium sponge in terms of a charge and smelting ingots either by an induction method in a cold crucible unit or by the combination of skull melting with subsequent vacuum-arc remelting. At the second pressure treatment stage during the acquisition of deformed semi-finished products with the required structure and shape memory effect properties, it is necessary to consider temperature-time conditions for the development of polygonization and recrystallization processes, as well as the precipitation of Ni-rich Ti3Ni4 intermetallics. [ABSTRACT FROM AUTHOR]

It is shown that the structure of alloys based on titanium nickelide, obtained by industrial technology, invariably contains titanium-rich phases of type Ti2Ni/Ti4Ni2(O, N), even if the nickel concentration in the B2-phase exceeds the equiatomic composition. The volume fraction of these phases depends on the smelting method, the purity of the charge, and the technology used for subsequent ingot processing. Regression equations linking shape recovery temperatures with the concentration of nickel in the B2-phase in the quenched state are presented. On the basis of these equations, a method for calculating the volume fraction of Ti3Ni4 type particles released during aging is proposed. [ABSTRACT FROM AUTHOR]