Nanostructured strain hardened aluminum-magnesium alloys modified by C₆₀ fullerene obtained by powder metallurgy. Part 1. Effect of magnesium concentration on the structure and phase composition of powders

This paper provides the first part of the study on the magnesium effect on the structural phase composition, physical and mechanical properties of nanostructured aluminum-magnesium composite materials with the composition Al_xMg_y + 0.3 wt.% C₆₀ fullerene. Composite powders were obtained by the simultaneous mechanical activation of initial materials in a planetary ball mill in an argon atmosphere. It was found that the obtained powders have a complex hierarchical structure made up of 50–200 μm aggregates consisting of 5–10 μm strong high-density agglomerates, which in turn are a combination of nanoscale (30–60 nm) crystallites. It was found that the increase in magnesium concentration in the composite up to 18 wt.% makes it possible to obtain crystallites with an average size of less than 30 nm during mechanical activation, while the size of aggregates is less than 50 μm. The maximum solubility of magnesium in aluminum with a crystallite size of 30–70 nm during mechanical activation was 15 wt.% (17 at.%). Using the differential scanning calorimetry method, it was found that nanostructured composites undergo irreversible structural phase transformations during heat treatment in a temperature range of 250–400 °C: recrystallization, decomposition of the α-solid solution of magnesium in aluminum and formation of intermetallic β-(Al₃Mg₂), γ-(Al₁₂Mg₁₇) and carbide (Al₄C₃) phases. In addition, the Raman spectra contain peaks that, according to some sources, correspond to covalent compounds of aluminum with C₆₀ fullerene – aluminum-fullerene complexes. The data obtained will be used in further research to determine parameters for the thermobaric treatment of nanocmposite powder mixtures in order to obtain and test bulk samples.

1. Estrin Y., Murashkin M., Valiev R. Ultrafine-grained aluminium alloys: processes, structural features and properties. In: Fundamentals of Aluminium Metallurgy. 2011. P. 468—503.

2. Lloyd D.J. Particle reinforced aluminium and magnesium matrix composites. Int. Mater. Rev. 1994. Vol. 39. No. 1. P. 1—23.

3. Markushev M.V., Bampton C.C., Murashkin M.Yu., Hardwick D.A. Structure and properties of ultra-fine grained aluminium alloys produced by severe plastic deformation. Mater. Sci. Eng. A. 1997. Vol. 234-236. P. 927—931.

4. Murashkin M.Yu., Kil’mametov A.R., Valiev R.Z. Structure and mechanical properties of an aluminum alloy 1570 subjected to severe plastic deformation by high-pressure torsion. Phys. Metals Metall. 2008. Vol. 106. No. 1. P. 90—96.

5. Popov M., Medvedev V., Blank V., Denisov V., Kirichenko A., Tat’yanin E., Zaitsev V. Fulleride of aluminum nanoclusters. J. Appl. Phys. 2010. Vol. 108. No. 9. P. 094317-1— 094317-6.

6. Evdokimov I.A., Perfilov S.A., Pozdnyakov A.A., Blank V.D., Bagramov R.Kh., Perezhogin I.A., Kulnitsky B.A., Kirichenko A.N., Aksenenkov V.V. Nanostructured composite materials based on Al—Mg alloy modified with fullerene C60. Inorg. Mater.: Appl. Res. 2018. Vol. 9. No. 3. P. 472—477.

7. Choi K., Shin S., Bae D., Choi H. Mechanical properties of aluminum-based nanocomposite reinforced with fullerenes. Trans. Nonferr. Met. Soc. China. 2014. Vol. 24. P. 47—52.

8. Maltseva T.V., Ozerets N.N., Levina A.V., Ishina E.A. Nonferrous metals and alloys: Тutorial. Ekaterinburg: Ural, 2019 (In Russ.).

9. Starink M. J., Zahra A.M. β’ and β precipitation in an Al— Mg alloy studied by DSC and TEM. Acta Mater. 1998. Vol. 46. No. 10. P. 3381—3397.

10. Siyuan L., Fusheng P., Kainer K. U., Yafang H., Wei K. Progress in light metals, aerospace materials and superconductors. Trans. Tech. Publ. Ltd, 2007.

11. Mukai T., Higashi K., Tanimura S. Influence of the magnesium concentration on the relationship between fracture mechanism and strain rate in high purity Al—Mg alloys. Mater. Sci. Eng. A. 1994. Vol. 176. No. 1-2. P. 181—189.

12. Schoenitz M., Dreizin E.L. Structure and properties of Al—Mg mechanical alloys. J. Mater. Res. 2003. Vol. 18. No. 08. P. 1827—1836.

13. Jie J.C., Zou C.M., Wang H.W., Li B., Wei Z.J. Mechanical properties of Al(Mg) solid solution prepared by so lidification under high pressures. J. Alloys Compd. 2012. Vol. 510. No. 1. P. 11—14.

14. Scudino S., Sakaliyska M., Surreddi K. B., Eckert J. Mechanical alloying and milling of Al—Mg alloys. J. Alloys Compd. 2009. Vol. 483. No. 1-2. P. 2—7.

15. Calka A., Kaczmarek W., Williams J.S. Extended solid solubility in ball-milled Al—Mg alloys. J. Mater. Sci. 1993. Vol. 28. P. 15—18.

16. Al-Aqeeli N., Mendoza-Suarez G., Drew R.A.L. XRD and TEM characterization of Al—Mg-based nanocomposite alloys. Rev. Adv. Mater. Sci. 2008. Vol. 18. P. 231—235.

17. Evdokimov I. A., Khayrullin R. R., Perfilov S. A., Pozdnyakov A. A., Bagramov R. H., Perezhogin I. A., Blank V. D. Nanostructured aluminum matrix composite materials, modified by carbon nanostructures. Mater. Today: Proceedings. 2018. Vol. 5. No. 12. P. 26153—26159.

18. Aborkin A.V., Evdokimov I.A., Vaganov V.E., Alymov M.I., Abramov D.V., Khor’kov K.S. Influence of mechanical activation mode on morphology and phase composition of Al—2Mg—nC nanostructured composite material. Nanotechnologies in Russia. 2016. Vol. 11. P. 297—304.

19. Gryaznov V.G., Kaprelov A.M., Romanov A.E. Size effects of dislocation stability in small particles and microcrystallities. Scripta Metal. 1989. Vol. 23. P. 1443—1448.

20. Rabinovich M.K., Markushev M.V., Murashkin M.Yu. Special features of formation of the submicrocrystalline structure in strain-heat treatment of aluminum alloy 1420 in different initial states. Met. Sci. Heat Treat. 1997. Vol. 39. No. 4. P. 172—176.

21. Lapovok R., Timokhina I., McKenzie P.W.J., O’Donnell R. Processing and properties of ultrafine-grain aluminium alloy 6111 sheet. J. Mater. Proc. Technol. 2008. Vol. 200. No. 1-3. P. 441—450.

22. Totten G.E., MacKenzie D.S. Handbook of aluminum. Vol. 1. Physical metallurgy and processes. Ohio: Marcel Dekker Inc., 2003.