OBTAINING FE-NI-CO-TI ALLOYS HAVING A THERMOELASTIC MARTENSITE-TRANSFORMATION

Using powder metallurgy methods, we have produced Fe-Ni-Co-Ti alloys t hat have a thermoelastic martensite transformation, which is the basis of the shape-memory effect manifested by such materials. Since pores are believed to improve the shape memory, specifically the reversible nature of the strain, attention was focused on development of the tech nology and investigation of the characteristics of porous Fe-Ni-Co-Ti alloys. The problems that arise during sintering of such alloys from s puttered powders are due to the chemical inhomogeneity of the initial structure and of the structure formed when the liquid phase appears. V arious forms of activation, such as cyclic sintering and a stepped inc rease in temperature, were used to prevent the liquid phase from appea ring. The properties of Fe-Ni-Co-Ti alloys with a shape memory effect can be improved if the porosity is increased by obtaining larger powde r grains with a more complicated shape.