High-purity titanium-nickel alloys with shape memory

Abstract

The invention includes an alloy containing equivalent amounts of nickel and titanium. The alloy has shape memory and a metallic purity of at least about 99.995%, and comprises less than about 200 ppm of gases. The invention also includes an alloy comprising titanium and nickel where the titanium and nickel amounts are non-equivalent. The alloy has shape memory and has a metallic purity of at least 99.995%, and contains less than about 200 ppm of gases. The invention further includes a method of producing a shape memory alloy. Titanium is provided having a metallic purity of at least 99.999% and nickel is provided having a metallic purity of at least 99.99%. The titanium and nickel are combined utilizing at least one melting event independently selected from e-beam melting, vacuum arc melting, vacuum induction melting, induction skull melting and plasma melting.

Description

RELATED PATENT DATA [0001] This patent claims benefit of priority under 35 U.S.C. §119 to U.S. Provisional Patent Ser. No. 60 / 514,317, which was filed Oct. 24, 2003.TECHNICAL FIELD [0002] The invention pertains to shape memory alloys and methods of producing shape memory alloys. BACKGROUND OF THE INVENTION [0003] Shape memory materials are materials which can recover a shape after heating. The shape memory properties of shape memory alloys such as, for example, nickel-titanium based shape memory alloys, can overlap with super-elastic properties. Super-elastic properties which exist over a temperature range specific to the particular material allow shape memory materials to have great flexibility. The unique properties of shape memory alloys make them particularly useful for applications in fields such as automotive, aerospace, thin-film, robotics, and medical fields. Exemplary applications for these materials include implantable medical devices, precision tools and medical instrumen...

AI Technical Summary

Benefits of technology

[0006] In one aspect the invention encompasses an alloy containing atomically equivalent amounts of nickel and titanium. The alloy

Problems solved by technology

For example, contaminants such as metallic impurities and / or gases can impair mechanical properties by forming inclusions that can lower fatigue life and can shift phase transformation temperatures out of specification.

The presence of such contaminants can also influence the effects of additional alloying elements, and can cause unpredictability, variability and inconsistency in mechanical and transformation properties of the resulting alloys.

Nickel-titanium alloys having limited purities attainable utilizing conventional methodologies typically have high work hardening rates which limit the cross-sectional reduction during many fabrication operations.

Further, the presence of contaminants can affect the biocompatibility of materials.