Mechanics of superelasticity in Ti–30Nb–(8–10)Ta–5Zr alloy

• Published in: Acta materialia 2010-06, Vol.58 (10), p.3557-3567
• Main Authors: Obbard, E.G., Hao, Y.L., Akahori, T., Talling, R.J., Niinomi, M., Dye, D., Yang, R.
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Martensitic phase transformation; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Shape memory alloys; Synchrotron radiation; Titanium alloys; X-ray diffraction
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2010.02.010

The superelastic behaviour of Ti–30Nb–10Ta–5Zr and Ti–30Nb–8Ta–5Zr (wt.%) biomedical alloys was investigated by tensile testing and in situ synchrotron X-ray diffraction. The phenomenological theory of martensite crystallography and texture prediction based on the Schmid law indicate that α ″ in Ti–30Nb–10Ta–5Zr forms in untwinned variants. Measurement of single-crystal elastic constants using an Eshelby–Kroener–Kneer self-consistent model shows that the 10-Ta alloy has a C ′ modulus 3 GPa higher than that of the 8-Ta alloy. That it nevertheless has a proof stress 35 MPa lower can be qualitatively explained by the differences in martensite crystallography. The results suggest that high tensile strength can be maintained for low modulus β -Ti in spite of martensitic transformation by optimizing transformation strains.