Microstructure of a Partially Crystallised Ti50Ni25Cu25 Melt-Spun Ribbon

A low dispersion of micrometric particles embedded in the amorphous matrix is obtained by controlled thermal treatments in an initially amorphous Ti50Ni25Cu25 melt-spun ribbon. The microstructure and crystallography of the crystalline particles have been investigated by means of TEM. Many of these particles are nearly spherical and exhibit a single crystallographic grain of austenite, the crystalline-amorphous interfaces revealing a stepped surface with preferential crystallographic planes. In addition to this, some particles with several grains in austenite have also been observed, most of them showing rather planar interfaces between adjacent grains in TEM images and twinning relationships in SAEDP. The experimental results indicate that the growth of the particular grains does not occur independently, and suggest that additional topological conditions, different from the twinning planes, yield the interfaces.