Dendritic Growth Characteristics of Cu-Rich Zone within Phase Separated Fe sub(50)Cu sub(50) Alloy

The undercooled Fe sub(50)Cu sub(50) alloy experiences a metastable liquid phase separation and separates into a Fe-rich zone and a Cu-rich zone within the gravity field. The growth characteristics of the Cu-rich zone were investigated by the glass fluxing method, and the achieved undercooling range was 20-261 K. The volume fraction of the Cu-rich zone decreases with the enhancement of the bulk undercooling. The microstructural morphologies of the Cu-rich zone are similar at all the undercooling conditions, that is, alpha Fe dendrites and particles are distributed inside (Cu) phase matrix. The secondary dendritic arm spacing of alpha Fe dendrites decreases with the increase in bulk undercooling. The growth mechanism of alpha Fe dendrites was analyzed by using the LKT/BCT dendritic growth theory. The dendritic growth in the Cu-rich zone is mainly controlled by solute diffusion so that the dendritic growth velocity is only several millimeters per second. Besides, the calculated results indicate that there is only inconspicuous solute trapping during the solidification of Cu-rich zone.