Peculiarities of microstructure of reactive diffusion zone in Al-Co system

Abstract

Microstructure and element composition of the sample having the multilayer reactive diffusion zone (RDZ) in Al-Co system obtained by means of contact smelting at 1375 °C for 1 hour were studied in cross-section by means of scanning electron microscopy and electron probe microanalysis (SEM-EPMA). In the multilayer RDZ the following intermetallic compounds CoAl₃, Co₂Al₅, CoAl, β' + (αСо), as well as solid solution of CoAl in (αСо) were identified using the spot energy-dispersion analysis (EDS). Using the methods of linear EDS and wave-dispersion (WDS) analyses the profiles of element concentrations were obtained. These concentration profiles indicate that CoAl₃, Co₂Al₅, CoAl and β' + (αСо) are able to form solid solutions in each other. Microstructural peculiarities of RDZ forming in the layers CoAl₃, Co₂Al₅, CoAl and β' + (αСо) can simulate the actual structural pattern of Al-Co alloys (as-cast).