¹MISiS National University of Science and Technology, Moscow, Russia ; ²Baykov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow, Russia:

Т. К. Akopyan, Research Fellow at the Department of Metal Forming^{1, 2}, e-mail: nemiroffandtor@yandex.ru

MISiS National University of Science and Technology, Moscow, Russia:
N. V. Letyagin, Post-Graduate Student at the Department of Metal Forming, e-mail: n.v.letyagin@gmail.com
V. V. Doroshenko, Post-Graduate Student at the Department of Metal Forming

With the help of the Thermo-Сalc software, the authors did thermodynamic calculations to examine the Al – Ca – Ni – Сe – Fe – Zr – Sc phase diagram. Alloys with optimum concentrations of calcium (4%), nickel (2%), cerium (2%) and a possible concentration of iron of up to 0.4% were selected for laboratory analysis. In the above range of concentrations, after the crystallization of primary dendrites (Al) one should expect to see a number of multiphase eutectic transformations. Thus, a double reaction L → (Al) + Al₉FeNi is followed by a triple reaction L → (Al) + Al₃Ni + Al₉FeNi and a quadruple reaction L → (Al) + Al₉FeNi + Al₃Ni + Al₄Ca, and the crystallization ends with a five-phase reaction L → (Al) + Al₁₁Ce₃ + Al₃Ni + Al₄Ca + Al₉FeNi. The total share of minor phases is at least 25 wt.%. That is why this alloy can be considered an aluminium matrix composite. The microstructural analysis of the as-cast base alloy Al₄Ca₂Ni₂Ce_0.4Fe and the alloys Al₄Ca₂Ni₂Ce_0.4Fe_0.4Zr and Al₄Ca₂Ni₂Ce_0.4Fe_0.2Zr_0.1Sc doped with zirconium and scandium was based on optical and scanning electron microscopy, as well as electron probe analysis. The obtained results show that the microstructure of the alloys in view is comprised of primary crystals (Al) and dispersed multiphase eutectic colonies. The calcium, nickel and cerium are concentrated in eutectic, and the scandium and zirconium – in eutectic and primary crystals (Al). The presence of zirconium and scandium in the as-cast (Al) makes dispersion hardening possible, which becomes the result of solid solution disintegration and further precipitation of coherent nanoparticles of the L1₂ — Al₃(Zr, Sc) phase during annealing. This process was investigated by measuring hardness of cast specimens during staged annealing. The maximum hardness (HV) can be achieved after the following procedure of staged annealing: 3 h at 300 ^oC plus 3 h at 350 ^oC. This can result in an over 20% increase in hardness in the alloy containing 0.20% Zr and 0.1% Sc.
The research was carried out with the financial support of the grant provided by the Russian Science Foundation (project No. 18-79-00345) (thermodynamic calculations, SEM, mechanical tests), as well as Fundamental Research Program 37P financed by the Presidium of the Russian Academy of Sciences (synthesis of alloys, TEM).

1. Knipling K. E., Karnesky R. A., Lee C. P., Dunand D. C., Seidman D. N. Precipitation evolution in Al – 0.1Sc, Al – 0.1Zr and Al – 0.1Sc – 0.1Zr (at.%) alloys during isochronal ageing. Acta Materialia. 2010. Vol. 58. pp. 5184–5195.
2. Clouet E., Barbu A., Lae L., Martin G. Precipitation kinetics of Al₃Zr and Al₃Sc in aluminum alloys modeled with cluster dynamics. Acta Materialia. 2005. Vol. 53. pp. 2313–2325.

3. Zhou W. W., Cai B., Li W. J., Liu Z. X., Yang S. Heatresistant Al – 0.2Sc – 0.04Zr electrical conductor. Materials Science and Engineering: A. 2012. Vol. 552. pp. 353–358.
4. Booth-Morrison C., Mao Z., Diaz M., Dunand D. C., Wolverton C., Seidman D. N. Role of silicon in accelerating the nucleation of Al₃(Sc, Zr) precipitates in dilute Al – Sc – Zr alloys. Acta Materialia. 2012. Vol. 60. Iss. 12. pp. 4740–4752.
5. Belov N. A., Naumova E. A., Akopyan T. K., Doroshenko V. V. Design of multicomponent alloys on the base of Al – Ca eutectics without requirement for quenching. Proceedings of the 16^th International Aluminum Alloys Conference (ICAA16). 2018.
6. Ikeshita S., Strodahs A., Saghi Z. Hardness and microstructural variation of Al – Mg – Mn – Sc – Zr alloy. Micron. 2016. Vol. 82. pp. 1–8.
7. Shurkin P. K., Akopyan T. K., Korotkova N. O., Tsydenov A. G., Finogeev A. S. Forming of the structure of rolled sheets made of the Al – Mn – Mg alloy with 0.3 %wt Zr produced from scrap cans made of alloy 3104. National Scientific Conference “Recent Advancements in Materials Science, Casting, Forming, Heat Treatment and Anticorrosion Protection of Light Alloys”. 2017. pp. 322–335.
8. Zolotorevskiy V. S., Belov N. A., Glazoff M. V. Casting aluminum alloys. Elsevier : Amsterdam, 2007. 544 p.
9. Belov N. A., Batyshev K. A., Doroshenko V. V. Microstructure and phase composition of the eutectic Al – Ca alloy, additionally alloyed with small additives of zirconium, scandium and manganese. Non-ferrous Metals. 2017. No. 2. pp. 49–54.
10. Belov N. A., Alabin A. N., Eskin D. G. Improving the Properties of Cold Rolled Al – 6% Ni sheets by alloying and heat treatment. Scripta Materialia. 2004. Vol. 50. Iss. 1. pp. 89–94.
11. Sims Z. C., Weiss D., McCall S. K., McGuire M. A., Ott R. T., Geer T., Rios O., Turchi P. A. E. Cerium-based, intermetallic-strengthened aluminum casting alloy: high-volume co-product development. Journal of the Minerals, Metals & Materials Society. 2016. Vol. 68. pp. 1940–1947.
12. Sims Z. C., Rios O., McCall S. K., Van Buuren T., Ott R. T. Characterization of nearnet-shape castable rare earth modified aluminum alloys for high temperature application. Light Metals 2016. Ed. by Williams E. Springer, Cham. pp. 111–114.
13. Cao Zujun, Kong Gang, Che Chunshan, Wang Yanqi, Peng Haotang. Experimental investigation of eutectic point in Al-rich Al – La, Al – Ce, Al – Pr and Al – Nd systems. Journal of Rare Earths. 2017. Vol. 35. pp. 1022–1028.
14. Sims Z. C., Rios O. R., Turchi P. E. A. et al. High performance aluminumcerium alloys for high-temperature applications. Materials Horizons. 2017. Vol. 4. pp. 1070–1078.
15. Weiss D., Rios O., Sims Z., McCall S., Ott R. Casting Characteristics of High Cerium Content Aluminum Alloys. Light Metals 2017. The Minerals, Metals & Materials Series. Ratvik A. (eds). Springer, Cham. pp. 205–211.
16. Belov N. A., Naumova E. A., Eskin D. G. Casting alloys of the Al – Ce – Ni System: Microstructural Approach to Alloy Design. Materials Science and Engineering: A. 1999. Vol. 271. pp. 134–142.
17. Goto Sh., Aso S., Komatsu Y., Belov N. A., Zolotorevsky V. S. Strength of eutectic alloys of the Al – Ce – Ni system. Izvestiya Vuzov. Tsvetnaya Metallurgiya. 2005. No. 5. pp. 40–47.
18. Kaufman J. G., Rooy E. L. Aluminum alloy castings: properties, processes, and applications. Ohio : ASM International, 2004. 321 p.
19. Belov N. A., Akopyan T. K., Mishurov S. S., Korotkova N. O. Effect of Fe and Si on the microstructure and phase composition of the aluminum-calcium eutectic alloys. Non-ferrous Metals. 2017. No. 2. pp. 37–42.
20. Belov N. A., Naumova E. A., Alabin A. N., Matveeva I. A. Effect of scandium on structure and hardening of Al – Ca eutectic alloys. Journal of Alloys and Compounds. 2015. Vol. 646. pp. 741–747.
21. 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.
22. Tian L., Kim H., Anderson I., Russell A. The microstructure-strength relationship in a deformation processed Al – Ca composite. Materials Science and Engineering: A. 2013. Vol. 570. pp. 106–113.
23. Belov N. A., Naumova E. A., Doroshenko V. V., Avxentieva N. N. Combined Effect of Calcium and Silicon on the Phase Composition and Structure of Al – 10 % Mg Alloy. Russian Journal of Non-Ferrous Metals. 2018. Vol. 59. No. 1. pp. 67–75.
24. Belov N. A., Naumova E. A., Akopyan T. K., Doroshenko V. V. Design of multicomponent aluminium alloy containing 2 wt% Ca and 0.1 wt% Sc for cast products. Journal of Alloys and Compounds. 2018. Vol. 762. pp. 528–536.
25. Chaubey A. K., Scudino S., Mukhopadhyay N. K., Khoshkhoo M. S., Mishrac B. K., Eckerta J. Effect of particle dispersion on the mechanical behavior of Al-based metal matrix composites reinforced with nanocrystalline Al – Ca intermetallics. Journal of Alloys and Compounds. 2012. Vol. 536. pp. 134–137.
26. Xue Y., Shen R., Ni S., Song M., Xiao D. Fabrication, microstructure and mechanical properties of Al – Fe intermetallic particle reinforced Al-based composites. Journal of Alloys and Compounds. 2015. Vol. 618. pp. 537–544.
27. Kim J. T., Hong S. H., Park J. M., Eckert J., Kim K. B. Microstructure and mechanical properties of hierarchical multi-phase composites based on Al – Ni-type intermetallic compounds in the Al – Ni – Cu – Si alloy system. Journal of Alloys and Compounds. 2018. Vol. 749. pp. 205–210.
28. Shurkin P. K., Belov N. A., Akopyan T. K., Alabin A. N., Aleshchenko A. S., Avxentieva N. N. Formation of the Structure of Thin-Sheet Rolled Product from a High-Strength Sparingly Alloyed Aluminum Alloy Nikalin. The Physics of Metals and Metallography. 2017. Vol. 118, Iss. 9. pp. 896–904.
29. Kendig K., Miracle D. Strengthening mechanisms of an Al – Mg – Sc – Zr alloy. Acta Materialia. 2002. Vol. 50. pp. 4165–4175.
30. Lefebvre W., Danoix F., Hallem H., Forbord B., Bostel A., Marthinsen K. Precipitation kinetic of Al₃(Sc, Zr) dispersoids in aluminium. Journal of Alloys and Compounds. 2009. Vol. 470. pp. 107–110.