Wires of superelastic nickel-titanium alloy and methods of forming the same
A nickel-titanium alloy with an average grain size of between 0.2 and 10 microns and a recoverable strain of greater than 9% is disclosed herein, in which the alloy is formed using a method which involves applying a shape set heat treatment to the nickel-titanium alloy. The heat treatment includes applying heat at a temperature between 225° C. and 350° C. for a period of time between 20 and 240 minutes.
1 . A nickel-titanium alloy having a recoverable strain of greater than 9% increase in length of an initial total length of the alloy, wherein the nickel-titanium alloy undergoes a residual elongation of less than 0.5% of the initial total length of the alloy in response to applying the recoverable strain and removing the recoverable strain such that the alloy recovers greater than 94% of the increased length resulting from the recoverable strain.
2 . The nickel-titanium alloy of claim 1 , wherein the nickel-titanium alloy has an upper plateau length of greater than 7%.
3 . The nickel-titanium alloy of claim 1 , wherein the nickel-titanium alloy has a lower plateau stress (LPS) of less than 250 MPa, wherein the LPS is measured in response to applying the recoverable strain to the nickel-titanium alloy.
4 . The nickel-titanium alloy of claim 1 , wherein the nickel-titanium alloy has an elongation at fracture of greater than 15% in length.
5 . The nickel-titanium alloy of claim 1 , further formed into an implantable medical device.