Effect of Ta on Microstructures and Mechanical Properties of NiTi Alloys

  • S. CaiEmail author
  • S.G. Mitchell
  • L. Wang
  • J. E. Schaffer
  • Y. Ren
Technical Article


Microstructures and mechanical properties of NiTiTa alloys with Ta contents of 5, 10 and 15 at.% were studied. It is found that, above the solubility limit of Ta, NiTiTa alloys consist of β-Ta, (TaTi)2Ni, Ti4Ni2O oxide and NiTi matrix. (TaTi)2Ni phase has a tetragonal crystal structure. It is brittle and broke up during processing. Ta in solution largely increases the phase transformation temperatures, while the extra Ta that forms secondary phases affects the phase transformation through its influence on residual internal energy. The volume fraction of β-Ta increases with increasing Ta content. Its ductility appears to be limited by tramp oxygen absorption. Although Ta addition largely improves the radiopacity of NiTiTa alloys, their future in medical applications may be impeded by the potential negative influences of brittle phases on ductility and fatigue performance.



SC and JES are thankful for the support from Fort Wayne Metals management on this fundamental research. SC thanks his colleagues D. Schoen and T. Ransom for SEM analysis and DSC testing. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE), Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DEAC02-06CH11357. Data analysis was performed by using the FIT2D and Maud software.


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Copyright information

© ASM International 2019

Authors and Affiliations

  • S. Cai
    • 1
    Email author
  • S.G. Mitchell
    • 1
  • L. Wang
    • 2
  • J. E. Schaffer
    • 1
  • Y. Ren
    • 3
  1. 1.Fort Wayne Metals Research Products CorpFort WayneUSA
  2. 2.Beijing Institute of TechnologyBeijingChina
  3. 3.X-ray Science Division, Argonne National LaboratoryArgonneUSA

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