National University of Science and Technology “MISIS”, Moscow, Russia:

N. A. Belov, Professor of a Chair Casting Technologies and art metal processing

¹National University of Science and Technology “MISIS”, Moscow, Russia ; ²Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow, Russia:

T. K. Akopyan, Researcher of Engineering Center “Casting Technologies and Materials”^1,2, e-mail: nemiroffandtor@yandex.ru

The most high-strength aluminum alloys based on the Al – Zn – Mg – (Cu) system have a significant tendency to form hot cracks during solidification. Additional alloying of 7xxx series alloys with the eutectic forming elements (Fe and Ni) that are slightly soluble in an (Al) solid solution was proposed in order to reduce the hot cracking tendency. In this case, the iron becomes an alloying element, rather than an harmful impurity. Since the appearance of primary crystals of the iron- and nickel-bearing phases is unacceptable, the boundaries of primary crystallization of (Al), Al₉FeNi, Al₃Ni and Al₃Fe phases (the liquidus projection) were computed using Thermo-Calc software. In accordance with the results of thermodynamic calculations of the multicomponent Al – Zn – Mg – Cu – Fe – Ni phase diagram, the new sparingly alloyed alloy ATs₆N_0.5Zh (Al – 6.3% Zn – 2.1% Mg – 0.2% Cu – 0.4% Fe – 0.6% Ni) based on the (Al) + Al₉FeNi eutectic was selected. The results of the fracture surface analysis of the castings after ageing show the mode of fracture is the dimple rupture. Traces of intergrain fracture typical for high-alloyed alloys of the 7xxx series without eutectic inclusions are not observed. Defect-free experimental samples with high mechanical properties (σ_r ~ 500 МPа, σ_0.2 ~ 450 МPа, δ ~ 4.7%) using liquid forging were obtained from the ATs₆N_0.5Zh alloy.

Research sponsored by the Ministry of Education and Science of the Russian Federation (Agreement 14.578.21.0039 (RFMEFI57814X0039)) in the framework of the Federal Target Program “Researches and developments on priority directions of scientific-technological complex of Russia for 2014–2020” and the grant of the Russian Federation President for Support of the Leading scientific schools, НШ-9899.2016.8.

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