Texture Engineering for Enhanced Flexibility In Nanocrystalline Medical Wire

Texture engineering is used to influence the elastic properties of Ø177 µm nanocrystalline medical wire toward a desirable outcome: improved flexibility via a reduced modulus of elasticity. It is known that implant grade alloy 35Ni-35Co-20Cr-10Mo (ASTM F562) is anisotropic such that the elastic modulus and other properties vary with crystal direction. Most cold drawn wire that is used in implanted devices contains some fiber texture that results in property variability. Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) are used to enumerate relevant microstructural data of texture-engineered and conventional wires. The observed elastic modulus is as much as thirty percent lower than published values for ASTM F562 alloy and correlates well with texture-based calculations. Strain-based fatigue data also show improved performance in the high cycle regime. The unique combination of high strength and flexibility may provide benefit in strain-controlled biomedical designs such as cardiac pacemaker lead wires.