Intelligent Design With Fine Diameter Nitinol Wire Over Wide Performance Spectra

The intent of this talk is to help bookend what is possible, and commercially replicable, in wire by alloy and process and thereby bring value and design choice clarity for the nitinol wire designer.  As design intelligence grows and device demands evolve, “plain vanilla” Ni_50.8Ti wire that is formed and shape-set at ~500C giving about 550 MPa onset stress, more than 7% recoverable strain, and excellent strain-fatigue durability at body temperature, though remarkable, can leave room for improvement.  Only a small fraction of the property tuning available in nitinol binary and ternary wire alloys has been used in the design of superelastic effect (SE) devices.  This is unremarkable in lieu of the need to simplify design choices in the face of an infinite array of design permutations on alloy, device structure and material process.  Still, a growing number next-gen applications including neurological guidewires and embolic stents are showing up with requirements of tuned onset stress, stiffness, functional fatigue, and radio-opacity to mention a few.  Past and new results in alternative processing of both binary and ternary alloys showcase a spectrum of possible properties with a focus on fine diameter wire, namely under 0.50 mm.