Materials having superelastic properties including related methods of fabrication and design for medical devices
There are super elastic NiTi materials for use as medical components, especially implantable medical components, and methods of fabricating such components to have desired R-phase characteristics in-vivo. Additionally, there are methods of processing a TiNi material to produce an implantable medical component by cold or warm working the TiNi material at least 15%; aging the cold or warm worked TiNi material under stress at between 300-700° C.; and further aging the TiNi material below 300° C. to produce desired R-phase characteristics. Additionally, there are methods of processing a TiNi material to produce a medical component by processing the TiNi material to produce a medical component that has a stress free M*s below a normal body temperature. Additionally, a TiNi material is used to produce a super elastic medical component from a tube, a sheet, a wire or a strip to have a stress free M*s below a normal body temperature.
1. A method of processing a TiNi material to produce an implantable medical component, comprising:
processing the TiNi material to produce a medical component by cold drawing, extruding or rolling, by aging heat treatments under stress in a range of 300° C. to 700° C. to achieve a desired shape of the implantable medical component and further aging at a temperature below 300° C. to produce a desired R-phase characteristic of depressing M p wherein the medical component has a stress free M*s below a normal body temperature, wherein a temperature separation of the stress free RP and Mp is at least 100° C.
2. The method of claim 1 wherein using use in-vivo at the normal body temperature the medical component contains at least some R-phase.
3. The method of claim 1 wherein a critical region of the medical component is substantially R-phase and Martensite.
4. The method of claim 3 wherein during a duty cycle applied during in-vivo use the medical component alternates between Martensite and R-phase.
5. The method of claim 1 wherein a temperature separation of the stress free R*p and M*p is at least 30° C.
6. The method of claim 1 wherein the TiNi material is a binary composition comprising Ti and Ni.
7. The method of claim 6 wherein the Ni atomic percentage is 50.5-51.5%.
8. The method of claim 1 wherein the TiNi material is a ternary composition comprising Ti and Ni and at least one other element.
9. The method of claim 1 wherein the TiNi material comprises more than 50% atomic Ni, from 0.1 to 3% of a Titanium substitution material with remaining composition comprising Ti wherein the Titanium substitution material is one of Hf, Zr, or Nb alone or in any combination.