Tsentr Sertifikatsii LLC, Moscow, Russia

E. P. Monakhova, Principal Specialist in Corrosion Protection, Candidate of Technical Sciences, e-mail: evmo444@ya.ru

National University of Science and Technology MISIS, Moscow, Russia
A. G. Rakoch, Professor at the Department of Steel Metallurgy, New Production Technologies and Metal Protection, Doctor of Chemical Sciences, Professor, e-mail: rakoch@mail.ru

D. P. Catenda, Postgraduate Student at the Department of Steel Metallurgy, New Production Technologies and Metal Protection
K. M. Al-Habib, Undergraduate Student at the Department of Steel Metallurgy, New Production Technologies and Metal Protection

RIFAR JSC, Gai, Russia
A. A. Lobach, Innovation Director, Candidate of Technical Sciences

A thermodynamic calculation was carried out that helped reveal the presence of intermetallic phases in AK12M2 and AK12pch silumins. The multicomponent alloy AK12M2 was found to contain a considerably greater number of crystallization phases, as well as secondary phases, which form after crystallization occurring at different rates, and ageing, respectively, than the AK12pch alloy. A thermodynamic calculation carried out in the JMatPro programme suggests a high probability that items made out of the AK12pch silumin only contain crystallization phases such as α-Al(Fe, Mn, Cr)Si and β-Al₅FeSi. Heaters were produced from the AK12M2 silumin by die casting using the technology of RIFAR JSC. According to thermodynamic calculations, the following stable phases of crystallization origin are present in the items: α-Al(Fe, Mn, Cr) Si, β-Al₅FeSi, Al₃Ti, γ-Al₇Cu₄Ni, Al₃Ni₂ and Q-Al₅Cu₂Mg₈Si₆ ; as well as metastable phases that are formed during ageing in a deoxygenated, slightly alkaline (pH 8.3) aqueous solution at a temperature of 90 ^oC (which is the maximum temperature for heating systems). The electron microprobe analysis (EMPA) data confirmed that the above thermodynamic calculations were correct. Because of their small sizes, metastable phases were not detected by EMPA. At the same time, according to the thermodynamic calculations, the share of metastable phase, in particular of θ'-Al₂Cu, can reach 1.58wt.% after approximately 41 days at 90 ^oC. Because of the high concentration of intermetallic compounds, the corrosion resistance of the AK12M2 alloy may differ from that of the AK12pch alloy in weakly alkaline aqueous solutions, which serve as the basic heat carrier in heating systems. The latter is due to the fact that most intermetallic compounds are cathodes and can significantly increase the corrosion rate of aluminium.

1. Kaufman J. G., Rooy L. E. Aluminum alloy castings: properties, processes and applications. Materials park : ASM International, 2004. 321 р.
2. Zolotorevskiy V. S., Belov N. A. Metallurgy of cast aluminium alloys. Moscow : Izdatelskiy dom MISIS, 2005. 376 p.
3. Belov N. A., Savchenko S. V., Belov V. D. Commercial silumins: Atlas of structures. Moscow : Izdatelskiy dom MISIS, 2009. 204 p.
4. GOST 1583–93. Aluminium casting alloys. Specifications. Introduced: 01.01.1997.
5. Murugarajan A., Raghunayagan P. The impact of pressure die casting process parameters on mechanical properties and its defects of A413 aluminium alloy. Metalurgija. 2019. Vol. 58. pp. 55–58.
6. Lee E., Mishra B. Effect of solidification cooling rate on mechanical properties and microstructure of Al – Si – Mn – Mg alloy. Materials Transactions. 2017. Vol. 58. pp. 1624–1627.
7. Capaccioli M. C. Terminale scambiatore di calore per impianto di riscaldamento ad acqua calda di uso civile : M. S. Thesis Alinea, Firenze, 2001.
8. Bean B., Olesen B. W., Woo Kim K. History of radiant heating & cooling systems — part 1. ASHRAE Journal. 2010. Vol. 52. pp. 40–47.
9. Rakoch A. G., Lobach A. A., Monakhova E. P., Begnarskii V. V. et al. Electrochemical and corrosion behavior of AK12M2 alloy in a model solution used in heating systems. International Journal of Corrosion and Scale Inhibition. 2022. Vol. 11, No. 3. pp. 1115–1130.
10. Volkova O. V., Dub A. V., Rakoch A. G., Gladkova A. A. et al. Experimental alloys Al6Ca, Al1Fe, Al6Ca1Fe vs commercial alloy AK12M2: Comparing their proneness to pitting corrosion. Corrosion and Metal Protection. 2017. No. 5. pp. 75–81.
11. Belov N. A., Naumova E. A., Akopyan T. K. Aluminium-based eutectic alloys: new alloying systems. Moscow : “Ore and Metals” Publishing House, 2016. 256 p.
12. Saunders N., Guo U. K. Z., Li X. et al. Using JMatPro to model materials properties and behavior. JOM. 2003. Vol. 55. pp. 60–65.
13. Yiwen Jian P., Zishuai Yu, Zhaohui Liu, Yi Li, Rui Li. Simulation study of impacts of radiator selection on indoor thermal environment and energy consumption. Engineering Proceedings. 2016. Vol. 146. pp. 466–472.
14. Dai S. et al. Design of new biomedical titanium alloy based on d-electron alloy design theory and JMatPro software. Transactions of Nonferrous Metals Society of China. 2013. Vol. 23, No. 10. pp. 3027–3032.
15. Arif M. A. M. et al. Effects of Cu and Mg on thixoformability and mechanical properties of aluminium alloy 2014. Transactions of Nonferrous Metals Society of China. 2020. Vol. 30, No. 2. pp. 275–287.
16. Yue C., Zheng B., Su M. et al. Effect of Cu/Mg ratio on the intermetallic compound and hot tearing susceptibility of Al – Cu – Mg alloys. International Journal of Metalcasting. 2023. Vol. 18. pp. 417–430.
17. Kumar S., Cracroft J., Wagstaff R. B. Influence of liquid jet stirring and in-situ homogenization on the intermetallics formation during DC casting of a 6xxx Al alloy rolling ingot. Light Metals. 2020. pp. 1013–1018.
18. Samat S. et al. Mechanical properties and microstructures of a modified Al – Si – Cu alloy prepared by thixoforming process for automotive connecting rods. Journal of Materials Research and Technology. 2021. Vol. 10. pp. 1086–1102.
19. Saunders N., Miodownik A. P. CALPHAD—Calculation of Phase Diagrams, Pergamon Materials Series. Oxford : Elsevier Science, 1998. Vol. 1, ed. R. W. Cahn. 479 p.
20. Belov N. A., Gusev A. Y., Eskin D. G. Evaluation of five-component phase diagrams for the analysis of phase composition in Al – Si based alloys. Zeitschrift für Metallkunde. 1998. Vol. 89, No. 9. pp. 618–622.
21. Lee E., Mishra B. Effect of solidification cooling rate on mechanical properties and microstructure of Al – Si – Mn – Mg alloy. Materials Transactions. 2017. Vol. 58, No. 11. pp. 1624–1627.