Engineers from Fort Wayne Metals, Indiana, reported in a presentation during SMST 2019 that they recently evaluated a composite comprised of a nickel-titanium matrix and varying amounts of tantalum fibers.
Previous studies had shown that niobium can largely increase martensitic transformation stresses, stiffness, and radiopacity of NiTi alloys, which are highly demanded by many medical applications. Nano sized niobium fibers embedded inside a nickel-titanium matrix can produce process-tunable hysteresis from narrow to wide, beneficial for applications ranging from high transformation stress vascular guidewires, to impact energy dissipation in automotive structures.
Tantalum is in the same group in the periodic table as niobium, but tantalum has a higher modulus and better radiopacity. Like niobium, it also forms a nearly pure secondary phase in the NiTi matrix during solidification.
In this study, a metal matrix composite comprising nitinol with varied tantalum area fractions was melted and processed to 0.50 mm diameter wires. Tensile and bending fatigue mechanical properties after various heat treatments were evaluated. In-situ synchrotron X-ray diffraction was used to investigate the stress-induced transformation behavior and the influences of tantalum fibers at the microscopic level. Results provide preliminary data to inform applied research in academia and industry.
Title: A Nitinol Tantalum Metal Matrix Composite for High Plateau Stress or Energy Dissipation
Authors: Dr. S. Cai, Dr. Jeremy E. Schaffer, Fort Wayne Metals Research Products Corporation, Fort Wayne, Indiana
https://www.asminternational.org/web/smst-2019/technical
