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Automated colour etching of aluminium alloys
EP39189
Poster Title: Automated colour etching of aluminium alloys
Submitted on 21 Sep 2022
Author(s): Ondřej Ambrož, Jan Čermák, Patrik Jozefovič, Šárka Mikmeková
Affiliations: Institute of Scientific Instruments of the Czech Academy of Sciences
This poster was presented at 56. Metallographie-Tagung Materialographie 2022
Poster Views: 144
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Poster Information
Abstract: Colour metallography of aluminium alloys can provide new structural knowledge or extend and refine structural knowledge compared to a black and   white image. The basic principle of colour metallography is to create a suitable film by etching. On samples coated with a suitable film, light interference is caused by the splitting of the incident light into components reflected at the air-layer interface and the layer-metal interface. The thickness of the film essentially determines at which colours the interference occurs. For films of suitable thickness, interference occurs in the blue, green and yellow regions. The film thickness depends on the chemical composition of the sample material, the chemical composition of the etchant and the etching time. If   the etching conditions are kept constant (etchant type, etching time) and the chemical composition of the individual micro-areas changes significantly, it will be possible to distinguish the micro-areas by colour contrast in the bright field. The results of colour etching of aluminium alloys in different types of   etchants will be presented. Using an automated apparatus, the same etching conditions will be maintained, including time and repeatability of   movements in the etching, cleaning and drying process.Summary: Automation can help achieve very good results in a process that is even highly susceptable and difficult to repeat. In the case of cast alloys, colour etching can produce very interesting images of the chemical segregation. In the case of wrought alloy, it would be preferable to anodize and observe the surface in polarized light to obtain better results. The development should be aimed at ensuring that a corectly prepared sample is not the product of chance but of controlled process.References: [1] Ambrož, O.; Čermák, J.; Mikmeková, Š.: Apparatus for automatic chemical etching of metallographic samples, in: Proc. 30th METAL Conf., Brno, Czech Republic
[2] Michna, Š.; Kuśmierczak, S.: Praktická metalografie, Univerzita J.E. Purkyně, Ústí nad Labem, Czech Republic, 2012
[3] Vander Voort, G.: Metallography, principles and practice, ASM International, Materials Park, Ohio, United States, 1999
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