Journals →  Non-ferrous Мetals →  2017 →  #2 →  Back

MATERIAL SCIENCE
ArticleName Microstructure and phase composition of the eutectic Al – Ca alloy, additionally alloyed with small additives of zirconium, scandium and manganese
DOI 10.17580/nfm.2017.02.09
ArticleAuthor Belov N. A., Batyshev K. A., Doroshenko V. V.
ArticleAuthorData

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

N. A. Belov, Professor of the Department of Metal Forming, e-mail: nikolay-belov@yandex.ru
V. V. Doroshenko, Post-Graduate Student of the Department of Metal Forming


Bauman Moscow State Technical University, Moscow, Russia:

K. A. Batyshev, Professor

Abstract

Using both thermodynamic calculations and experimental analyses, the Al – Ca – Mn – Fe – Zr – Sc phase diagram near the aluminum corner has been studied. Based on the obtained results, the optimal concentrations of calcium (about 4%) and manganese (about 0.7%) at an allowable iron content of up to 0.3–0.4% were chosen. According to the thermodynamic calculations, during solidification of the Al4Ca0.7Mn0.4Fe alloy, after formation of a the (Al) primary crystals, the eutectic reaction L → (Al) + Al6(Fe, Mn) should occur. Solidification of this alloy should be completed via the ternary eutectic reaction L → (Al) + Al6(Fe, Mn) + Al4Ca. The addition of 0.2–0.4% zirconium should leads to the formation of primary crystals of the Al3Zr aluminide. However, it is known that at the cooling rates typical for the casting in metal moulds (5–20 oC/s), the concentration boundary is shifted toward higher zirconium concentrations. Therefore, it was assumed that the total amount of Zr should enter into the (Al) composition and consequently have no influence on the phase composition of the alloy. When zirconium addition is present, the casting temperature should be higher than for the base alloy. The microstructure of two alloys with different content of zirconium and scandium: Al4Ca0.7Mn0.4Fe0.2Zr0.1Sc and Al4Ca0.7Mn0.4Fe0.4Zr was examined by means of optical microscopy, scanning electron microscopy and by electron microprobe analysis. The obtained results have revealed that for both alloys microstructure consists of the (Al) primary crystals and eutectic colonies with a fine structure. Calcium and iron are concentrated in the eutectic, while scandium, zirconium and manganese were detected in the both eutectic composition and (Al) primary crystals. Analysis of the hardness and specific electrical conductivity together with transmission electron microscopy has revealed that joint alloying with zirconium and scandium (0.20% Zr and 0.1% Sc) leads to the precipitation hardening due to the decomposition of (Al) and further precipitation of the coherent L12 – Al3(Zr, Sc) phase nanoparticles. The highest hardness is observed after step annealing at 250 oC, 3 h plus 300 oC, 3 h.

The work was supported by the Russian Science Foundation grant 14-19-00632P.

keywords Al – Ca alloys, Al3(Zr, Sc) nanoparticles, thermodynamic calculations, phase transformations, microstructure, annealing, hardening
References

1. 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.
2. Belov N., Naumova E., Akopyan T. Eutectic alloys based on the Al – Zn –Mg – Ca system: microstructure, phase composition and hardening. Materials Science and Technology. 2017. Vol. 33. pp. 656–666.
3. Swaminathan K., Padmanabhan K. A. Journal of Materials Science. 1990. Vol. 25. pp. 4579–4586.
4. Belov N. A., Naumova E. A., Akopyan T. K., Doroshenko V. V. Phase Diagram of Al – Ca – Mg – Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content. Metals. 2017. Vol. 7(10). p. 429.
5. Kaufman J. G., Rooy E. L. Aluminum alloy castings: properties, processes, and applications, ASM International, Ohio, 2004.
6. Hatch J. E. (Ed.), Aluminum: properties and physical metallurgy, ASM International, Ohio, 1984.
7. Marquis E. A., Seidman D. N. Nanoscale structural evolution of Al3Sc precipitates in Al (Sc) alloys. Acta Materialia. 2001. Vol. 49. pp. 1909–1919.
8. Costa S., Puga H., Barbosa J., Pinto A. M. P. The effect of Sc additions on the microstructure and age hardening behaviour of as cast Al–Sc alloys. Materials and Design. 2012. Vol. 42. pp. 347–352.
9. 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.
10. 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.
11. 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.
12. 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.
13. 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. pp. 4740–4752
14. 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
15. Kendig K., Miracle D. Strengthening mechanisms of an Al – Mg – Sc – Zr alloy. Acta Materialia. 2002. Vol. 50. pp. 4165–4175.
16. 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. pp. 4740–4752
17. Kaufman J. G., Rooy E. L. Aluminum alloy castings: properties, processes, and applications, ASM International, Ohio, 2004.
18. Vlach M., Stulikova I., Smola B., Piesova J., Cisarova H., Danis S., Plasek J., Gemma R., Tanprayoon D., Neuber V. Effect of cold rolling on precipitation processes in Al – Mn – Sc – Zr alloy. Materials Science and Engineering A. 2012. Vol. 548. pp. 27–32.

Full content Microstructure and phase composition of the eutectic Al – Ca alloy, additionally alloyed with small additives of zirconium, scandium and manganese
Back