Influence of Thermo-Mechanical Processing Conditions on Phase Transformation Temperatures of Nitinol Annuloplasty Rings

Shape setting is a particular thermo-mechanical process used to imprint the desired shape in Nitinol (NiTi) shape memory alloy semi-finished products. It is a critical step as it must simultaneously ensure precise shape definition and specific transformation temperatures (TTs), on which the achievement of functional properties is based. Once a shape setting treatment has been optimized, it becomes highly relevant in industrial production to assess whether the same parameters can be applied to components with different geometries, therefore involving different mold designs. This study investigates the influence of mold geometry on the TTs of NiTi tubes, shape set to obtain different kinds of annuloplasty rings. Starting from the same tube batch and applying identical heat treatment parameters, two mold designs were used to impart different shapes and the phase transformation behavior was investigated. The results show that mold geometry does not significantly affect the TTs, indicating that the same shape setting parameters can be applied across different component geometries.