Evaluating the Effect of Homogenization Temperature and Time on the Microstructure of Alloy AlCu4MgMn by Electron Microscopy and x-Ray Fluorescence Analysis

Homogenizing annealing is a method of heat treatment that entails keeping a semifinished product at a high temperature close to the liquidus temperature (roughly 0.7–0.8 of the melting point) to eliminate chemical heterogeneity through diffusion processes. Segregation is caused by selective crystallization, which results in a gradual change in the composition of the solid phase. During cooling of the ingot, low temperatures initiate the growth of crystal nuclei in accordance with the general laws that govern crystallization. As a result, each solidified layer has a different chemical composition. The concentrations of the elements in the solid phase are low initially and very high at the end. The susceptibility of the alloy to crystalline segregation is greater, the wider the range of temperatures over which it crystallizes and the greater the horizontal distance between the liquidus and solidus lines. The crystalline structure also becomes more nonuniform with an increase in the concentration of the alloying elements. In the experimental alloys studied in this investigation, the degree of nonuniformity increased when the content of the alloying elements was between 6 and 9%. Crystalline segregation can be eliminated by diffusion of the elements during homogenizing annealing.