Zofia Kwak, Aldona Garbacz-Klempka, Małgorzata Perek-Nowak

Microstructure of selected 7xxx series aluminum alloys obtained by semi-continuous casting


The study was conducted for two selected 7xxx series aluminum alloys according to PN-EN 573-3:2010 - Polish version. The analysis of ingots was carried out on 7003, 7003S and 7010, 7010K alloys with a similar ratio of zirconium content. Symbols S and K are our internal modifications, still compatible with the standard. The ingots were made by semi-continuous casting. Aluminum alloys of this series, with improved properties, are intended for plastic-processing.
The aim of this publication is to show how the microstructure of ingots is being formed during semi-continuous casting. The chemical profiles of ingots were determined using optical emission spectroscopy. Chemical analysis in micro-areas with evaluation by scanning electron microscope SEM with EDS analyzer was performed and the distribution of chemical elements in the microstructures are also presented. An XRD detector was used to show specific phases in the alloys.
The grains are formed in a particular way during crystallization. In the middle of the ingot - further away from the crystallizer - the grains are larger. Semi-continuous casting together with homogenization enables the production of ingots with uniform cross sections as can be seen in the paper.

Keywords: Al-Zn-Mg-Cu alloys, DC casting, quality of ingots, microstructure, micro-structural analysis with scanning electron microscope with included SEM-EDS, phase composition by X-Ray Diffraction (XRD),
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