Investigation of Thermal and Mechanical Properties of Various Superelastic Nitinol Alloy Systems

Nitinol alloy composition as well as mechanical and thermal properties are critical attributes for designing medical devices. Ternary alloys such as Ni-Ti-Cr or Ni-Ti-Co are often selected because of their increased modulus and plateau strength. However, these ternary alloys do not meet the chemistry per ASTM F2063. For device manufacturers who look to improve the performance of legacy binary alloy parts, this makes ternary alloys a difficult choice due to regulatory concerns.

This study investigates how the Ni-Ti chemistry and raw material transformation temperatures impact the finished wire performance. Test methods used to evaluate the wires will be bend moment, three-point bend, uniaxial tension testing, bend and free recovery. This data will assist the purchaser of binary Ni-Ti to request the proper alloy and specification limits to meet the desired properties for their device.