Microstructural changes in welded Zn–Al alloy

Abstract

Extruded eutectoid Zn–Al alloy was welded by a melt of the same eutectoid alloy. Two different microstructures were observed in the joint part and in the bulk of the welded alloy. Typical dendritic structure of as-cast Zn–Al alloy was observed in the joint part of the welded alloy. The bulk of the welded Zn–Al alloy appeared as fine grain structure. Two different metastable phases, η′_T decomposed from η′_s of the chilled as-cast state and η′_E of the extruded state, were found to be unstable during the early stages of aging. A four-phase transformation occurred after the decompositions of these two metastable phases of η′_T. Microstructures of both the joint part and bulk of the welded alloy were investigated simultaneously during the aging processes.