Nitinol Post-Shape-Setting Time Temperature Transformation (TTT) and Time Temperature Stress (TTS) Properties

Abstract The tuning of Nitinol components to achieve target transformation temperatures and mechanical properties requires careful selection of shape-setting recipes. We explore the roles of melt chemistry, raw material manufacturer, material type (wire vs. tube), heat treatment modality (air furnace vs salt), heat treatment times (1–120 min), and temperatures (350–550 °C) on the resultant transformation temperature and plateau stresses of Nitinol components. Through the compilation of hundreds of recipe permutations, we constructed time–temperature-transformation (TTT) diagrams and time–temperature-stress (TTS) diagrams which provide predictive tools to assist Nitinol medical device designers.