Liquid phase separation in undercooled Co-Cu alloys processed by electromagnetic levitation and differential thermal analysis

The phase separation in the metastable miscibility gap of undercooled Co-Cu alloys has been investigated by electromagnetic levitation (EML) and diffe rential thermal analysis (DTA). The boundary line of the miscibility gap co uld be determined from DTA experiments through the exothermic process of se paration. The separation morphologies of the levitated samples show drastic difference from those observed in the DTA-processed samples, which is attr ibuted to the electromagnetic stirring effect and different cooling rates. The concentrations of the two separated phases determined from the solidifi ed EML-processed samples agree well with the miscibility gap boundary measu red by DTA. The statistical population of Go-rich spheres in the levitated specimens gives indication that the undercooling level has significant infl uence on coalescence of the minority phase. (C) 2001 Elsevier Science B.V. All rights reserved.