Phase transformations and precipitation in amorphous Ti sub 50 Ni sub 25 Cu sub 25 ribbons

Phase transformations and precipitation mechanisms in Ti sub 50 Ni sub 25 Cu sub 25 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 approx470 deg C after which the orthorhombic B19 martensite is formed on cooling. Annealing up to 700 deg C yield the identification of Cu sub 3 Ti sub 2 and Ti sub 2 Ni 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.