Phase transformations and precipitation in amorphous Ti50Ni25Cu25 ribbons

Phase transformations and precipitation mechanisms in Ti50Ni25Cu25 material, starting from an amorphous planar-cast ribbon, were studied by in-situ transmission electron microscopy (TEM). On heating, the cubic B2 austenite crystallisation occurs around 470°C after which the orthorhombic B19 martensite is formed on cooling. Annealings up to 700°C yield the identification of Cu3Ti2 and Ti2Ni precipitates. These precipitations drastically alter the matrix composition, resulting in the formation upon cooling of the monoclinic B19′ martensite with different types of long-period stacking sequences. Also the B19′ martensite is still recognised in the latter samples.