| 摘要 |
<p>The invention relates to a process for preparing shape memory materials of the type of intermetallic NiTi compound alloyed with Fe, Cu or Nb, each of them having a purity of 99.9%, by combining the mechanical grinding process with the reactive synthesis, employed in industry for pipe or tube couplings, for making fastening devices in the shape of clamps or tenons, in robotics, for actuators, in heat engines used in power engineering or for making various medical devices. According to the invention, the process consists in grinding a mixture of powders comprising 32...49% Ni, at a grain size of less than 10μm, and 36...46% Ti, at a grain size of less than 100μm, the percentage being expressed by weight, the mixture being then alloyed with Cu or Fe powder, at a grain size of less than 71μm, or Nb powder, at a grain size of less than 125μm, whereto 1...2% stearic acid or Zn stearate is admixed as homogenization binder, the grinding taking place within a mill having stainless steel bowl and grinding bodies, at a powder/balls charging ratio of 1/5, in both directions, while changing the direction of rotation after one hour of work and 10 min of rest, in a humid medium of ether or petroleum and an argon protected atmosphere of 99.9% purity, at a rotation speed of 250...450 rpm, the alloying time ranging between 10...20 hours, depending on the alloying element, the powders being compressed in rectangular or cylindrical moulds, at pressures ranging between 3...6 tf/cm, after which a tempering and homogenization thermal treatment is applied for 2...4 hours, at a temperature of 450°C, under argon atmosphere, followed by non-shock furnace chilling, the material being finally calibrated by pressing at a pressure 1.5...2 times greater than the compaction pressure.</p> |
