SHS Processing of NiTi-Nb Smart Alloys
Nb additions to NiTi smart alloys are known to lead to the PTT-hysteresis broadening and transformation temperatures raising – required in numerous applications. As Nb has a high affinity for oxygen, NiTi-Nb alloys processing by powder metallurgy, via SHS, from elemental Ni-Ti-Nb powder mixtures, seems to be more advantageous and cost-effective than by classical one. However, its application encounters difficulties determined by the NiTi higher Gibbs Free Energy of Formation than of Ni3Ti and NiTi2, possible Ni-Nb compounds formation, Nb acting as diluent in SHS. This research proved the possibility to overcome these difficulties and of NiTi-Nb alloys obtaining by SHS using energetically activated powder mixture by controlled Mechanical Alloying. Also, it was proved the possibility to reduce Nb content from the common one of 9 at.% to 5 at.% without a significant effect of transformation temperatures and hysteresis decreasing.
Ionel Chicinaş and Liviu Brânduşan
R. L. Orban et al., "SHS Processing of NiTi-Nb Smart Alloys", Materials Science Forum, Vol. 672, pp. 175-178, 2011