A Ni-free β-Ti alloy with large and stable room temperature super-elasticity

A Ni-free β-Ti alloy comprising Ti-40Hf-13Nb-4.5Sn (wt.%) was developed as a substitute for NiTi (nitinol) alloys in medical applications. It is found that, due to significant Stress Induced Martensite (SIM) transformation and large lattice transformation strain, combined with good strength and stability, this alloy showed large and stable super-elastic deformation behavior at room temperature. Total recoverable strain of 5.3 % was obtained at 6% deformation. According to preliminary data, mechanical properties and fatigue performance of this alloy are within the neighborhood of super-elastic NiTi alloys. Plateau strengths can be further tuned to a wide range by low temperature aging similar to Ni-rich binary NiTi. It can be manufactured in large industrial scales by commercial production lines, has been melted in hundreds of kilogram scale, and is relatively easy to shape set into device subcomponent forms. With additional characteristics such as relatively high X-ray visibility, good corrosion resistance and biocompatibility, this alloy provides a superelastic option in Ni-sensitive dental, orthodontic, orthopedic bone staple, and neurovascular applications to name a few possibilities.