High temperature shape memory effect in ruthenium alloys

摘要

The shape memory effect is displayed by near-equiatomic ruthenium alloys of Ta or Nb with compositions of TaxRu1-x where x can be as low as 0.38 and preferably x=0.44 to 0.63 and NbxRu1-x where x can be as low as 0.25 and preferably x=0.45 to 0.59 which exhibit a transition from the high-temperature cubic phase to a tetragonal phase. These alloys are prepared by melting together tantalum and ruthenium, or niobium and ruthenium, in the above mentioned ratios. A further embodiment of this invention is to alloy NiTi alloys with, one of these two ruthenium-based high-temperature alloys (i.e. either Ta-Ru or Nb-Ru) so as to obtain a similar behavior which will result in an increase in the transition temperature relative to unalloyed Ni-Ti. Articles having the shape memory effect are prepared by forming the alloy into a desired shape above the transition temperature, or alternatively, imparting the desired shape to the alloy below the transition temperature by machining or other shaping processes, and then deforming the alloy into a different shape at a temperature below the transition temperature.