Metastable solidification pathways of undercooled eutectic CoSi–CoSi2 alloys.

Solidification and growth behavior of undercooled eutectic CoSi–CoSi 2 melts was observed using containerless levitation and in situ high-energy synchrotron X-ray diffraction techniques. Three metastable solidification pathways of eutectic CoSi–CoSi 2 were determined as a function of undercooling. Upon double recalescence at low undercoolings the primary and secondary phases are CoSi and CoSi 2 , while at high undercoolings the phase formation sequence is reversed. At intermediate undercoolings a single recalescence was observed and attributed to a crossover of the nucleation barriers for the two phases. Scanning electron microscopy combined with electron back-scattering diffraction measurements revealed changes of the morphological characteristics and orientation of CoSi and CoSi 2 phases for different solidification pathways. Image 1 [ABSTRACT FROM AUTHOR]