Hot Forming of Nitinol: Fundamental Investigations and Applications

Nitinol's thermomechanical properties are well studied and understood below the so-called martensite death (MD) temperature, above which martensite cannot be induced by mechanical stress: Even at high stresses Nitinol stays in the austenite phase. This paper presents tensile tests performed well above MD (>150 °C) with Nitinol specimens laser cut from tube. The investigations show that Nitinol drastically changes its mechanical properties in this temperature range: The superelastic plateau shortens and finally vanishes. Furthermore, Nitinol starts becoming more ductile.