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

N. A. Belov, Professor, Director of Engineering Center “Innovation cast technologies and materials”, e-mail: nikolaybelov@yandex.ru
A. N. Alabin, Senior Researcher, Head of Department of Engineering Center “Innovation cast technologies and materials”
A. A. Yakovlev, Post-Graduate Student

Influence of up to 7.5% of copper on formation of cast microstructure of aluminum alloys, containing 1% (wt.) of Mn, was studied, using calculated and experimental methods. Flat ingots (1040180 mm section) were obtained by casting into graphite mould (cooling rate after casting was about 15 K/s). Ingots were annealed, according to multistage modes, in the temperature range of 300–540 ^oC, with a step of 50 ^oC (or 40 ^oC) and 3 h holding at each stage. Polished samples, cut from the central part of the ingots (cast and annealed), were studied. The structure was examined in optical microscope (OM, Axiovert 200 MMAT) and scanning electron microscope (SEM, JSM-6610LV). Calculations of phase composition (including unequilibrium solidification, Sheil-Gulliver simulation) were made, using Thermo-Calc software (version TCW-5, database TTAL5). There was found that morphology of eutectic of Al₂Cu phase in cast state strongly depends on copper concentration in alloy. According to this, morphology varies from globular inclusions (<3% of Cu) to elongated veins (>4% of Cu). A good coincidence between calculated and experimental data was established, according to the number of eutectic (Al) + Al₂Cu. There was studied the influence of copper on electrical conductivity (γ) of experimental alloys in cast state and after various annealing conditions in the temperature range of 300–540 ^oC. There was shown that increase of copper concentration in the alloy in annealed condition (especially at 400 ^oC) leads to increase of  γvalue. Obtained data shows that optimum copper content is 1.0–1.5% (wt.). On one hand, such concentration enables to obtain a favorable microstructure of cast condition for deformation processing without usage of homogenization treatment of ingots. On the other hand, the concentration facilitates the complete allocation of manganese in the form of secondary phase precipitates Al₂₀Cu₂Mn₃, which make a positive influence on the heat resistance of alloys.

1. GOST 4784–97. Alyuminiy i splavy alyuminievye deformiruemye. Marki (State Standard 4784–97. Aluminium and aluminium deformed alloys. Grades). Introduced: 2000–07–01.
2. Belov N. A., Alabin A. N. Armaturostroenie — Valve Industry. 2010. No. 2. pp. 50–54.
3. Anthony U. U., Ellyott F. R., Boll M. D. Alyuminiy. Svoystva i fizicheskoe metallovedenie : spravochnik (Aluminium. Properties and physical metallurgy : reference book). Edited by John E. Hatch. Translated from English. Moscow : Metallurgiya, 1989. 324 p.
4. Mondolfo L. F. Struktura i svoystva alyuminievykh splavov : perevod s angliyskogo (Structure and properties of aluminium alloys : translation from English). Moscow : Metallurgiya, 1979. 483 p.
5. Struktura i svoystva polufabrikatov iz alyuminievykh splavov : spravochnik (Structure and properties of half-finished products, made of aluminium alloys : reference book). Under the editorship of V. I. Elagin, V. A. Livanov. Moscow : Metallurgiya, 1984. 408 p.
6. Dobatkin V. I., Elagin V. I., Fedorov V. M. Bystrozakristal lizovannye alyuminievye splavy (Rapidly crystallized and aluminium alloys). Moscow : All-Russia Institute of Light Alloys, 1995. p. 341.
7. Belov N. A., Alabin A. N. Microstructure and mechanical properties of Al – Cu – Mn cold rolled sheet alloys. Aluminium Alloys: Their Physical and Mechanical Properties : Proceedings of 11^th International Conference of Aluminium Alloys. Under the editorship of J. Hirsch, B. Scrotzki, G. Gottstein. Aachen, 2008. pp. 1653–1659.
8. Fedorov V. M. Tekhnologiya legkikh splavov — Technology of light alloys. 1993. No. 2. pp. 67–81.
9. Kolobnev I. F. Zharoprochnost liteynykh alyuminievykh splavov (Heat-resistance of light aluminium alloys). Moscow : Metallurgiya, 1973. 320 p.
10. Belov N. A. Fazovyy sostav alyuminievykh splavov (Phase composition of aluminium alloys). Moscow : «MISiS» Publishing House, 2009. 392 p.

11. Toleuova A. R., Belov N. A., Smagulov D. U., Alabin A. N. Quantitative analysis of the Al – Cu – Mn – Zr phase diagram as a base for deformable refractory aluminum alloys. Metal Science and Heat Treatment. November, 2012. Vol. 54, Iss. 7/8. pp. 402–406.
12. Belov N. A., Zolotorevskij V. S. Al – Cu – Mn – Zr – Cr creep resisting alloys: microstructure and mechanical properties. Advances in the metallurgy of aluminum alloys : proceedings. James T. Staley Honorary Symposium on Aluminum Alloys (from ASM Material Solution Conference). Under the editorship of M. Tiryakioglu. Ohio, 2001. pp. 425–431.
13. Terzi S., Salvo L., Suery M., Dahle A., Boller E. In situ microtomography investigation of microstructural evolution in Al – Cu alloys during holding in semi-solid state. Transactions of Nonferrous Metals Society of China. 2010. No. 20. pp. 734–738.
14. Jang J.-H., Nam D.-G., Park Y.-H., Park I.-M. Effect of solution treatment and artificial aging on microstructure and mechanical properties of Al – Cu alloy. Transactions of Nonferrous Metals Society of China. 2013. No. 23. pp. 631–635.
15. Belov N. A., Alabin A. N., Prokhorov A. Yu. Izvestiya vuzov. Tsvetnaya metallurgiya — Russian Journal of Non-Ferrous Metals. 2009. No. 4. pp. 42–47.