Biocompatible copper-based single-crystal shape memory alloys

摘要

We describe herein biocompatible single crystal Cu-based shape memory alloys (SMAs). In particular, we show biocompatibility based on MEM elution cell cytotoxicity, ISO intramuscular implant, and hemo-compatibility tests producing negative cytotoxic results. This biocompatibility may be attributed to the formation of a durable oxide surface layer analogous to the titanium oxide layer that inhibits body fluid reaction to titanium nickel alloys, and/or the non-existence of crystal domain boundaries may inhibit corrosive chemical attack. Methods for controlling the formation of the protective aluminum oxide layer are also described, as are devices including such biocompatible single crystal copper-based SMAs.

主权项

1. A method of forming a biocompatible anisotropic, single crystal copper-aluminum shape memory alloy having hyperelastic properties, the anisotropic single crystal shape memory alloy material formed being deformable at a constant force at recoverable strain of at least 9% with a very narrow loading-unloading hysteresis, a recovery which is completely repeatable and complete and a very low yield strength when martensitic, the method comprising the steps of:
forming a single crystal copper-aluminum-based shape memory alloy from a seed of copper aluminum based alloy aligned on the <100> crystallographic direction; in a surface region of depth greater than 1 nm below an exposed outer surface of the single crystal copper-aluminum-based shape memory alloy, diffusing aluminum atoms into the surface region to enrich the surface region in aluminum relative to copper; and forming a controlled layer of aluminum oxide on the single crystal copper-based shape memory alloy by oxidizing the aluminum atoms in the surface region.