Solidification study of spray formed aluminum alloys

Abstract

Aluminum processed by casting are usually alloyed with silicon, copper and magnesium; the first one increases the fluidity of the alloy, while the last two give the possibility of hardening the material through heat treatment. The spray forming applied to these alloys has been proposed by our research group in order to increase its value at recycling. Once processed, they can be mechanically formed, increasing the range of possibilities for use beyond the casting industry, for example in products of higher value and responsibility that demands primary aluminum, which request a lot of energy to be produced. Thus, the spray forming has been a promising technique, since even having contaminants originating from previous processing, it is obtained a refined microstructure which ensures an alloy with high mechanical properties. Regarding this subject, one of the main topic under discussion in the scientific community is the way as the spray formed solidification of metal alloys occurs. In this sense, our research group recently published an article: Zepon, G .; Ellendt, N .; Bolfarini, C. Solidification Sequence of Spray-Formed Steel. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, vol. 47, n. 2, p. 842-851, 2016, which is a new insight related to the prevalent mechanisms in the solidification of spray formed alloys. However, this article was based on experiments with steel. This project aims to study the solidification of spray formed aluminum alloys. For this purpose, it will be studied three compositions with different levels of complexity: Al-6.0%Si, Al-6.0%Si-3.0%Cu and Al-6.0%Si-3.0%Cu-1.0% Fe. The last composition described is the basis of one of the main alloys used for casting in the automotive industry, the A319, which together with a similar alloy composition with 9% of Si represents more than 80% of aluminum alloys used in casting. In order to achieve these purposes it will be analyzed the phases presented in the microstructure (optical microscopy and scanning electron microscopy) in addition with thermodynamic simulation, in order to check aspects such as phase stability, partition coefficients and the amount of phases present in equilibrium. It can be mentioned that this project is included in a FAPESP Thematic project no. 2013 / 05987-8: Processing and characterization of amorphous metal alloys, metastable and nano-structured, in the item related to aluminum alloys recycling.