Microstructure of Cu-Fe base alloy powders produced by conventional gas atomization was investigated and an egg-type core structure consisting of two or triple layers was obtained in the alloy systems which have a stable miscibility gap in the liquid phase. It was found that the minor liquid phase, which is dependent on the chemical composition of the alloy, always forms the core in a powder, assembling to the center of the powder. The origin of the formation of this core microstructure can be explained by Marangoni motion on the basis of the temperature dependence of the interfacial energy between the Fe- and Cu-rich liquid phases.
In principle, since the egg-type powder may be formed not only in alloy systems, but also in immiscible ceramics and polymer systems, it is expected for this new type of powder with the core structure to be utilized for various technical applications, such as electrical, chemical, magnetic parts, etc.
