JSC Arconic 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 Science2, Candidate of Technical Sciences, e-mail: ar-evgenii@yandex.ru

JSC Arconic SMZ, Moscow, Russia:

A. M. Drits, Director for Business Development and New Technologies, Candidate of Technical Sciences, e-mail: Alexander.Drits@arconic.com

The study addresses the effect of hafnium on microstructure, mechanical properties and stability of Al3Sc type strengthening particles in Al – Mg system 01570 alloy with scandium and zirconium additions. As part of the study, 01570 alloy-based ingots with hafnium content of 0.1% and 0.2% (here and everywhere hereinafter % weight is indicated) were cast in steel chill molds with zirconium and without zirconium addition. The obtained ingots grains size was examined using optical microscope. It was established, that 0.2% Hf addition to the previously designed 01570 alloy can reduce the average nominal grain diameter by half. A number of anneals was performed at temperatures of 400 ^oC and 450 ^oC with 1, 10, 30 minutes, 1, 4, 8, 16, 32 and 56 hours soaking times, to study the rate of supersaturated solid solution decomposition and determine the moment of strengthening dispersed particles coalescence onset. Annealed samples were measured for microhardness, electrical resistance and examined using scanning electron microscopy. It was demonstrated, that samples with hafnium do not lose strengthening phase stability at traditional treatment temperature of 400 ^oC with considerable soaking time (up to 56 h), at 450 ^oC decrease in microhardness is observed only after 4 hours of soaking. The samples were pressure-formed, i.e., hot and cold rolled, to determine recrystallization onset, it was established, that even at 500 ^oC and short soaking period (up to 30 minutes) rolled samples with hafnium still have some not recrystallized microstructure, while the samples without hafnium have visible equiaxed recrystallized grains. Using transmission electron microscope, it was possible to establish that the dispersed particles obtained in the alloy with 0.2% Hf retain a size of about 9 nm after the treatment cycle, and the average distance between them is 62 nm.
The study was supported by a grant from the Russian Science Foundation, project 18-79-10099.

1. Filatov Yu. A., Plotnikov A. D. Structure and properties of deformed semifinished products from 01570C aluminum alloy of the Al – Mg – Sc system for a product of RSC Energia. Tekhnologiya legkikh splavov. 2011. No. 2. pp. 15–26.
2. 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.
3. Yashin V. V., Aryshenskiy V. Yu., 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.
4. 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.
5. Zakharov V. V., Rostova T. D. Effect of scandium, transition metals and impurities on the hardening of aluminum alloys during the solid solution decomposition. Metallovedenie i termicheskaya obrabotka metallov. 2007. No. 9. pp. 12–19.
6. Elagin V. I., Zakharov V. V., Rostova T. D. Scandium alloyed aluminum alloys. Metallovedenie i termicheskaya obrabotka metallov. 1992. No. 1. pp. 24–28.
7. Skachkov V. M. Chemical alloying with scandium, zirconium and hafnium alloys based on aluminum: Dissertation … of Candidate of Chemical Sciences. Yekaterinburg, 2013.
8. Konkevich V. Yu., Nikolas A. V.. High-strength thermally non-strengthened alloy and method for its production. Patent RF No. 2636781C2. Applied: 25.12.2015. Published: 28.11.2017. Bulletin No. 34.
9. Hallem H., Marthinsen K., Lefebvre W., Danoix F., Forbord B. The formation of Al3(Sc_xZr_yHf_{1 – x – y})-dispersoids in aluminium alloys. Materials Science and Engineering: A. 2006. Vol. 421. No. 1-2. pp. 154–160.
10. Knipling K. E., Karnesky R. A. , Lee C. P., Dunald D. C. Precipitation evolution in Al – 0.1 Sc, Al – 0.1 Zr and Al –0.1 Sc–0.1 Zr (at.%) alloys during isochronal aging. Acta Materialia. 2010. Vol. 58. No. 15. pp. 5184–5195.
11. Belov N. A., Alabin A. N. Promising aluminum alloys with additions of zirconium and scandium. Tsvetnye Metally. 2007. No. 2. pp. 99–106.
12. Hori S., Furushiro N. Structure of rapidly solidified Al – Hf alloys and its thermal stability. Proceedings of the 4^th international conference on rapidly quenched metals. Osaka University. Sendai, Japan, 24–28 August 1981. pp. 1525– 1528.
13. Rokhlin L. L., Bochvar N. R. Physicochemical studies of aluminum alloys with several transition metals. All materials. Enziklopedichesiy spravochnik. 2014. No. 2. pp. 35–42.
14. GOST 9450–76 (ST SEV 1195–78). Measurements microhardness by diamond instruments indentation. Introduced: 01.01.1977.
15. Kubaschewski O., Von Galdbeck. Phase diagram Hf – Al. Hafnium: Physico-chemical properties of its compounds and alloys. Atomic Energy Review. Special issue. 1981. No. 8. pp. 58–60.
16. Napalkov V. I., Makhov S. V. Alloying and modifying aluminum and magnesium. Moscow: MISiS, 2002. 374 p.