JSC Arсoniс SMZ, Samara, Russia

V. V. Yashin, Manager, e-mail: Vasiliy.Yashin@arconic.com

I. A. Latushkin, Leading Specialist, e-mail: Ilya.Latushkin@arconic.com

Samara National Research University, Samara, Russia:
E. V. Aryshensky, Associate Professor of the Chair for Metal Technology and Aviation Materials Science, Candidate of Technical Sciences, e-mail: ar-evgenii@yandex.ru
D. A. Stozharov, Student of the Chair for Technology of Metals and Aviation Materials Science, e-mail: dimastozharov@yandex.ru

The objective of the study is to determine kinetics of L1₂ structure type particles precipitation in Al – Mg system aluminum alloys, containing scandium and zirconium. The article addresses microstructure evolution of scandium containing alloys, including two-component alloy and Al – Mg system alloys, containing multiple components, i.e., 1565ch alloy (Al – Mg – Mn – Zn – Zr system) and 01570 alloy (Al – Mg – Mn – Sc – Zr system). The samples were produced by casting in water chilled copper permanent mold. Analysis of the samples, representing various alloys, including 99.95% pure aluminum, confirmed quantitative data of solutes effect on electrical resistance. The optimal homogenization modes, enabling max alloying components dissolution in aluminum matrix, were established for the studied alloys. After that the samples were subjected to heterogenization annealing in the temperature range from 250 ^oC to 450 ^oC, with soaking time ranging from 1 to 106 s. C-curves of supersaturated solid solution decomposition were plotted based on correlation of samples electrical resistance in max saturated solution and after annealing under different modes; it was demonstrated, that decomposition curves of the alloys, containing 0.2 and more scandium, have two peaks, at 300 ^oC and at 425 ^oC. The obtained data are approximated by power functions (min determination coefficient R2 is 0.97), which are helpful for such alloys thermomechanical treatment modelling. It is demonstrated, that during cast samples heat treatment at the temperature above 350 ^oC decomposition of alloys, containing 0.2% and more scandium, is associated with secondary crystallization, and decomposition product distribution is fan-shaped, confirming the theory of discontinuous decomposition, observed by other researchers in similar alloys. The size of L1₂ structure particles, generated during discontinuous decomposition, ranged from 50 to 270 nm, which is significantly different from the optimal values of 40–50 nm.
The study was supported by a grant from the Russian Science Foundation, project 18-79-10099.

1. Drits M. E., Toropova L. S., Bykova Yu. G., Elagin V. I., Filatov Yu. A., Zakharov V. V., Zolotorevsky Yu. S., Makarov A. G. USSR copyright certificate No. 704266. Aluminum based alloy. 1979.
2. Elagin V. I. Alloying wrought aluminum alloys with transition metals. Moscow: Metallurgiya, 1975.
3. Yashin V. V., Aryshenskiy V. Yu., Latushkin I. A., Tepterev M. S. Substantiation of a manufacturing technology of flat rolled products from Al – Mg – Sc based alloys for the aerospace industry. Tsvetnye Metally. 2018. No. 7. pp. 75–82.
4. Yashin V. V., Aryshenskiy E. V., Kolbasnikov N. G., Tepterev M. S., Latushkin I. A. Effect of microalloying with transition and rare earth metals of the aluminum – magnesium system on mechanical properties during thermomechanical treatment. Proizvodstvo prokata. 2017. No. 8. pp. 42–48.
5. Aryshenskiy E. V., Grechnikova A. F., Yashin V. V., Tepterev M. S. Effect of microalloying of alloys of the aluminum – magnesium system with rare earth and transition metals on the structure evolution during thermomechanical treatment. Proizvodstvo prokata. 2017. No. 4. pp. 4–11.
6. Zakharov V. V., Filatov Yu. A., Teleshov V. V. Works of JSC VILS in the field of creating wrought aluminum alloys based on new alloying systems. Tekhnologiya legkikh splavov. 2018. No. 4. pp. 16–23.
7. Mann V. Kh. et. al. Effect of heat treatment modes on the structure and mechanical properties of rolled sheets of the Al – Mg alloy with a scandium content of 0.1wt.%. Tsvetnye metally i mineraly. 2018. pp. 727–735.
8. Zakharov V. V. Stability of scandium solid solution in aluminum. MiTOM. 1997. No. 2. pp. 15–20.
9. Røyset J., Ryum N. Kinetics and mechanisms of precipitation in an Al – 0.2 wt.% Sc alloy. Materials Science and Engineering: A. 2005. Vol. 396, No 1-2. pp. 409–422.
10. Berezina F. L., Volkov V. A., Domashnikova B. P., Chuistov K. V. Some features of the decomposition of a supersaturated solid solution of alloys of the Al – Sc system. Metallofizika. 1987. Vol. 9, No. 5. pp. 43–45.
11. Jo H. H., Fujikawa S. I. Kinetics of precipitation in Al₃Sc alloys and low temperature solid solubility of scandium in aluminium studied by electrical resistivity measurements. Materials Science and Engineering: A. 1993. Vol. 171, Iss. 1-2. pp. 151–161.

12. Fujikawa S.-I., Sakauchi S. Kinetics of precipitation in Al–0.2% mas. Sc alloys. Proc. 6^th Int. Conf. On “Aluminum alloys”. Toyohashi. Japan. July 1998. pp. 805–810.
13. Murray J. L. The Al – Sc (aluminum-scandium) system. Journal of Phase Equilibria and Diffusion. 1998. Vol. 19, No. 4. pp. 380–384.
14. Johansen A. Microstructures and properties of aluminium-magnesium alloys with additions of manganese, zirconium and scandium. Trondheim : Norwegian University of Science and Technology, 2000. 230 p.
15. Wolter R., Siebert P., Fabian H. G. The description of the isothermal decomposition processes in AlSc alloys by means of electric resistivity measurements and TEM investigations. Crystal Research and Technology. 1993. Vol. 28, Iss. 1. pp. 63–72.
16. Novikov I. I. Theory of heat treatment of metals: a textbook for universities. 4^th edition revised and enlarged. Moscow: Metallurgiya, 1986. 480 p.
17. Blake N., Hopkins M. A. Constitution and age hardening of Al – Sc alloys. Journal of Materials Science. 1985. Vol. 20, Iss. 8. pp. 2861–2867.
18. Norman A. F., Prangnell P. B., McEwen R. S. The solidification behaviour of dilute aluminium–scandium alloys. Acta Materialia. 1998. Vol. 46, No. 16. pp. 5715–5732.
19. Norman A. F., Tsakiropoulos P. Rapid solidification of Al – Hf alloys: solidification microstructures and decomposition of solid solutions. International Journal of Rapid Solidification. 1991. Vol. 6, No. 3-4. pp. 185–213.