A Nitinol Tantalum Metal Matrix Composite for High Plateau Stress or Energy Dissipation
Our previous studies showed that Nb can largely increase martensitic transformation stresses, stiffness and radiopacity of NiTi alloys, which are highly demanded by many medical applications. Nano sized Nb fibers embedded inside a NiTi 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. Being in the same group in the periodic table as Nb, Ta has a higher modulus and better radiopacity. Like Nb, 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 Ta area fraction are melted and processed to 0.50 mm diameter wires. Tensile and bending fatigue mechanical properties after various heat treatments are evaluated. In-situ synchrotron X-ray diffraction is used to investigate the stress-induced transformation behavior and the influences of Ta fibers at the microscopic level giving preliminary data to inform applied research in academia and industry.