Wires of nickel-titanium alloy and methods of forming the same
A wire of a nickel-titanium alloy having a permanent set of less than 5% when 11% strain is applied to the wire is disclosed. The wire may be formed by applying a first heat treatment to the wire, the first heat treatment includes applying heat of a first temperature for a first period of time, applying a strain deformation to the wire to set a shape for the wire during the first heat treatment, and applying a second heat treatment to the wire. The second heat treatment includes applying heat of a second temperature different from the first temperature for a second period of time, and the second temperature is between 210° C. and 290° C. The wire may have a modulus of at least 53 GPa when 200 MPa of stress is applied to the wire, and the wire is bonded to a secondary component.
1. A wire of a nickel-titanium alloy having a permanent set of less than 5% in length when 11% strain is applied to the wire, the wire having a modulus of at least 53 GPa when 200 MPa of stress is applied to the wire, wherein the modulus is calculated based on a tensile stress and a tensile strain of the wire.
2. The wire of claim 1 , wherein the permanent set is less than 1% when the 11% strain is applied to the wire.
3. The wire of claim 1 , wherein the modulus is at least 55 GPa.
4. The wire of claim 1 , wherein the modulus is between 53 GPa and 64 GPa.
5. The wire of claim 1 , wherein the modulus decreases by at least 5 GPa when 400 MPa of stress is applied to the wire.
6. The wire of claim 5 , wherein the modulus decreases by at least 10 GPa when 400 MPa of stress is applied to the wire.
7. The wire of claim 5 , wherein the modulus decreases by a value of between 5 GPa and 16 GPa when 400 MPa of stress is applied to the wire as compared to when 200 MPa of stress is applied to the wire.
8. The wire of claim 1 , further having a lower plateau stress (LPS) of at least 350 MPa, wherein the LPS is measured in response to applying a reversible strain to the wire.
9. The wire of claim 1 , further formed into an implantable medical device.
10. The wire of claim 9 , wherein the medical device is: a stent-graft, an embolic filter, a septal occlude, or a heart valve.
11. A wire of nickel-titanium alloy formed by a method comprising:
applying a first heat treatment to the wire, the first heat treatment including applying heat of a first temperature between 450° C. and 550° C. for a first period of time;
applying, during the first heat treatment, a strain deformation to the wire to set a shape for the wire; and
applying a second heat treatment to the wire following the first heat treatment without applying the strain deformation between the first heat treatment and the second heat treatment, or during the second heat treatment, the second heat treatment includes applying heat of a second temperature different from the first temperature for a second period of time, the second temperature being between 210° C. and 290° C.
12. The wire of claim 11 , wherein the first heat treatment further comprises one or more additional heat treatment processes operable to set a shape of the wire.
13. The wire of claim 11 , wherein the second period of time is between 5 minutes and 40 minutes.
14. The wire of claim 11 , wherein a first elasticity of the wire resulting from the first heat treatment is within 2% of a second elasticity of the wire resulting from the second heat treatment.
15. The wire of claim 11 , wherein a second hysteresis of the wire resulting from the second heat treatment is at least 40 MPa lower than a first hysteresis of the wire resulting from the first heat treatment.
16. The wire of claim 11 , wherein a second lower plateau stress (LPS) of the wire resulting from the second heat treatment is at least 30 MPa higher than a first LPS of the wire resulting from the first heat treatment.
17. The wire of claim 11 ,
wherein a second permanent set of the wire resulting from the second heat treatment is at least 85% lower than a first permanent set of the wire resulting from the first heat treatment, and
wherein each of the first and second permanent sets is defined by a length of the wire after a strain of 11% is applied to the wire.
18. The wire of claim 11 having a permanent set of less than 5% in length when 11% strain is applied to the wire.
19. The wire of claim 18 , wherein the permanent set is less than 1% when the 11% strain is applied to the wire.
20. The wire of claim 11 , wherein after the first heat treatment, the wire has a first modulus of less than 42 GPa when 200 MPa of stress is applied to the wire, and after the second heat treatment, the wire has a second modulus of at least 55 GPa when 200 MPa of stress is applied to the wire.
21. The wire of claim 20 , wherein the second modulus is between 55 GPa and 64 GPa.
22. The wire of claim 11 , further having a lower plateau stress (LPS) of at least 350 MPa.
23. The wire of claim 11 , further formed into an implantable medical device.
24. The wire of claim 23 , wherein the medical device is: a stent-graft, an embolic filter, a septal occlude, or a heart valve.
25. A method of forming a wire of a nickel-titanium alloy, the method comprising:
applying a strain deformation to the wire to set a shape for the wire;
applying a first heat treatment to the wire following the applying the strain deformation, the first heat treatment including applying heat of a first temperature between 450° C. and 550° C. for a first period of time; and
applying a second heat treatment to the wire following the first heat treatment without applying the strain deformation between the first heat treatment and the second heat treatment, or during the second heat treatment, wherein applying the second heat treatment includes applying heat of a second temperature different from the first temperature for a second period of time, the second temperature being between 210° C. and 290° C.
26. The method of claim 25 , resulting with a wire having a LPS of at least 350 MPa after the second heat treatment.
27. The method of claim 25 , wherein the second period of time is between 5 minutes and 40 minutes.
28. The method of claim 25 , wherein a first modulus of the wire resulting from the first heat treatment is within 2% of a second modulus of the wire resulting from the second heat treatment.
29. The method of claim 25 , wherein a first elasticity of the wire resulting from the first heat treatment is within 2% of a second elasticity of the wire resulting from the second heat treatment.
30. The method of claim 25 , wherein a second hysteresis of the wire resulting from the second heat treatment is at least 40 MPa lower than a first hysteresis of the wire resulting from the first heat treatment.
31. The method of claim 25 , wherein a second lower plateau stress (LPS) of the wire resulting from the second heat treatment is at least 30 MPa higher than a first LPS of the wire resulting from the first heat treatment.
32. The method of claim 25 ,
wherein a second permanent set of the wire resulting from the second heat treatment is at least 85% lower than a first permanent set of the wire resulting from the first heat treatment,
wherein each of the first and second permanent sets is defined by a length of the wire after a strain of 11% is applied to the wire.
33. The method of claim 25 ,
wherein a second permanent set of the wire resulting from the second heat treatment is less than 1%,
wherein each of the first and second permanent sets is defined by a length of the wire after a strain of 11% is applied to the wire.
34. The method of claim 25 , wherein the resulting wire has a permanent set of less than 5% in length when 11% strain is applied to the wire.
35. The method of claim 34 , wherein the permanent set is less than 1% when the 11% strain is applied to the wire.
36. The method of claim 25 , wherein after the first heat treatment, the wire has a first modulus of less than 42 GPa when 200 MPa of stress is applied to the wire, and after the second heat treatment, the wire has a second modulus of at least 55 GPa when 200 MPa of stress is applied to the wire.
37. The method of claim 36 , wherein the second modulus is between 55 GPa and 64 GPa.
38. The method of claim 25 , wherein the resulting wire has a lower plateau stress (LPS) of at least 350 MPa.
39. The method of claim 25 , further comprising forming the wire into an implantable medical device after the second heat treatment is applied.
40. The method of claim 39 , wherein the medical device is: a stent-graft, an embolic filter, a septal occlude, or a heart valve.