Effect of Nb addition on martensitic transformation behavior of AuTi-15Co based biomedical shape memory alloys

Hyunbo Shim, Masaki Tahara, Tomonari Inamua, Kenji Goto, Yoko Yamabe-Mitarai, Hideki Hosoda

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


The effect of quaternary addition of Nb being from 0 to 2 mol% on the phase constitution, phase transformation behavior and shape memory behavior of Au-50 mol%Ti-15 mol%Co (AuTiCo) alloys is studied. X-ray diffraction analysis shows that, with increasing Nb concentration, the primary phase appeared at room temperature changes from B19 orthorhombic martensite phase to B2 cubic parent phase, and that all the lattice parameters are not largely changed by Nb addition. The maximum transformation strain evaluated in 2 mol%Nb-added AuTiCo is 7.4%. Differential scanning calorimetry revealed that the reverse martensitic transformation finish temperature (Af ) decreases from 414K in Nb-free AuTiCo to 303K by 2 mol%Nb addition. The ratio of Af change by Nb addition is evaluated to be -55K/mol%Nb, that is comparably larger than -31K/mol%Nb in NiTi. These results indicate that Nb addition is effective to stabilize B2 parent phase. AuTiCo alloy containing less than 2 mol%Nb exhibits shape memory effect with 90% shape recovery ratio. Besides, AuTiCo containing 2 mol%Nb exhibits 2.8% superelastic shape recovery at room temperature as well as 7.4% maximum transformation strain. Therefore, Nb addition to AuTiCo is effective to decrease the martensitic transformation temperature and to improve superelasticity, although the transformation temperature hysteresis increases by Nb addition, similar to Nb-added NiTi.

Original languageEnglish
Pages (from-to)429-434
Number of pages6
JournalMaterials Transactions
Issue number3
Publication statusPublished - 2015
Externally publishedYes


  • AuTiCo
  • Biomedical shape memory alloys
  • Martensitic transformation behavior
  • Niobium addition
  • Shape memory effect
  • Superelasticity

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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