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ArticleName Influence of silicon on the structure and properties of high-strength cast aluminum alloy AZ5NF
DOI 10.17580/tsm.2021.08.09
ArticleAuthor Matveev S. V., Fokin D. O., Ryabov D. K.

Institute of Light Materials and Technologies Ltd., Moscow, Russia:

S. V. Matveev, Director of the department for Foundry Alloys1, Candidate of Technical Sciences, e-mail:
D. O. Fokin, Project Manager
D. K. Ryabov, Director of Science


The phase composition and the mechanical properties of the AZ5NF with various contents of silicon impurities alloy were investigated by both calculation and experimental methods. For evaluation of the alloy phase composition and the effect of the chemical composition, CALPHAD method integrated in Thermo-Calc software was applied. Further scanning electron microscopy technique a significant increase of the volume fraction of Mg2Si phase with an increase of silicon content from 0.1% to 0.3%. It is shown that in case of silicon content higher than 0,2 wt.% Mg2Si phase starts forming during equilibrium crystallization. This phase forms as the thin layers at the grain boundaries. This leads to brittle intergranular fracture and significant reduction of the alloy ductility both in the as-cast state and in T6 temper. Based on this limits for the silicon content in AZ5NF have been proven. It is shown that dissolution of Mg2Si phase (full or partial depending on silicon content) requires solid solution treatment. Following quenching and artificial ageing provide high strength and ductility.

keywords Aluminum alloys, silicon, impurity, phase composition, crystallization, plasticity, hardening, heat treatment

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