Complex microstructural changes in as-cast eutectoid Zn-Al alloy

Abstract

Phase transformations and microstructural changes of an as-cast eutectoid Zn-Al alloy (ZnAl22Cu2) were investigated during isothermal holding. The typical dendritic structures consisted of α′s phase as a core with the edge of decomposed β′s phase and decomposed η′s in the interdendritic regions. A series of complex phase transformations was observed. Both decompositions of β′s and η′s were determined at an early stage of ageing and a four-phase transformation, αf+ɛ→T′+η, was observed at the boundaries of αf phase and the ɛ phase, instead of clearly observed at the boundaries of ɛ phase, in a solution-treated Zn-Al alloy during prolonged ageing.