Microstructural characterisation in non-dendritic Al-Si-Mg (356/357) alloy feedstocks

Abstract

Microstructural characterisation carried out on four non-dendritic feedstocks in the as received and reheated conditions has revealed that the transition from dendritic to non-dendritic occurs through the formation of ripened dendrites, rosettes and ripened rosettes. Formation of divorced eutectic is observed during the initial stages of remelting in all the alloys. Electrical conductivity measurement can be used as an instantaneous non-destructive evaluation (DE) tool to assess the presence of divorced eutectic. The eutectic entrapped inside the primary alpha globules is finer than that present outside. Feedstock, which is neither grain refined nor modified, requires longer holding time to obtain the non-dendritic microstructure on remelting.