Colour Metallography of Cast Aluminium Alloys
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Laura García
Abstract
For better observation of the microstructure of cast aluminium alloys under an optical microscope, the contrast obtained for the different micro constituents was enhanced by making use of a copper phthalocyanine based colorant. The proposed method allows distinguishing structural details which would remain hidden or poorly resolved when studying the conventionally etched sample. The method produces high relief for silicon precipitates with the tint further accentuating the outlines, allowing detection of morphology change of the aluminium-silicon eutectic due to chemical modification with strontium. Magnesium micro segregations in the α-aluminium phase, caused by incorrect thermal treatment during ageing, can also be clearly distinguished. The coloured images obtained by optical microscopy are very sharp and provide similar or better information than the corresponding Scanning Electron Microscopy images. The method proved to be suitable for Quality Control in the fabrication of cast aluminium alloy compounds, sourcing down possible errors to different stages of the process.
Kurzfassung
Zur besseren Beobachtung des Mikrogefüges von Aluminiumgusslegierungen unter einem Lichtmikroskop wurde der Kontrast der verschiedenen Mikrobestandteile durch Verwendung eines Farbstoffs auf Kupferphthalocyaninbasis verbessert. Die vorgeschlagene Methode ermöglicht die Unterscheidung struktureller Details, die bei Untersuchung einer konventionell geätzten Probe verborgen geblieben oder unzureichend aufgelöst gewesen wären. Mit diesem Verfahren wird ein Hochrelief der Siliziumausscheidungen erzeugt, wobei die Färbung die Konturen betont und der Nachweis von morphologischen Veränderungen des Aluminium-Silizium-Eutektikums durch chemische Modifizierung mit Strontium möglich ist. Auch Magnesium Mikroabscheidungen in der α-Aluminium-Phase, die durch unsachgemäße Wärmebehandlung im Zuge der Vergütung verursacht werden, lassen sich deutlich erkennen. Die mittels optischer Mikroskopie erzielten Farbbilder sind sehr scharf und liefern ähnliche oder bessere Informationen, als die entsprechenden rasterelektronenmikroskopischen Aufnahmen. Dieses Verfahren erwies sich als geeignet für die Qualitätskontrolle in der Herstellung von Verbindungen aus Aluminiumgusslegierung, da mögliche Fehler bis zu den verschiedenen Prozessphasen zurückverfolgt werden können.
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© 2014, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- Characterization of Frictional Stressed White Etching Layers out of Cutting Tools by Means of Transmission Electron Microscopy (TEM)
- Grain Size Measurement in Experimental Co-Re-based Alloys to Study Grain Coarsening, Part I
- Colour Metallography of Cast Aluminium Alloys
- Failure Analysis of EN24 Steel Shear Bolt Used in Space Programme
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- Characterization of Frictional Stressed White Etching Layers out of Cutting Tools by Means of Transmission Electron Microscopy (TEM)
- Grain Size Measurement in Experimental Co-Re-based Alloys to Study Grain Coarsening, Part I
- Colour Metallography of Cast Aluminium Alloys
- Failure Analysis of EN24 Steel Shear Bolt Used in Space Programme
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
