Eutectic channelling in a squeeze cast Al-4.5Wt%Cu alloy

• Published in: Scripta metallurgica et materialia 1995-05, Vol.32 (10), p.1553-1557
• Main Authors: Gallerneault, M., Durrant, G., Cantor, B.
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solidification
• ISSN: 0956-716X
• DOI: 10.1016/0956-716X(94)00030-L

The extent of macrosegregation occuring during the squeeze casting of a simple cylindrical shape in an Al-4.5wt.%Cu alloy was investigated. The alloy was prepared by inductively melting commercial purity aluminum and a master alloy of Al-50wt.%Cu under argon. Optical metallographic evaluation was carried out on the squeeze cast samples. The application of 100 Mpa pressure during solidification caused an increase in the heat transfer coefficient and thereby leading to a smaller dendrite size. Shorter dendrites, faster freezing rates and smaller interdendritic channels all hindered solute back flow and inverse segregation. They therefore promoted normal degregation, i.e. solute depletion close to the die walls and solute enrichment at the centre of the casting. In Al-4.5wt.%Cu the eutectic had a greater density than the average melt composition and it sank, impinging upon advancing dendrites below and gave a distinctive V shape. The presence of a variety of phases in the V-channels was thought to be typical of the solidification that might be anticipated in a highly partitioned melt, where local variations in the microstructure were often observed.