Study of the heat treatment effect on the structure and mechanical properties welded joints of aluminum-lithium alloys V-1461 and V-1469

The use of rare earth elements for alloying of aluminum alloys is a promising direction nowadays — filler materials doped with rare earth metals (REM) improve the mechanical properties of welded joints of high-strength aluminum-lithium alloys compared to serial filler material. The results of studying the effect of the composition of alloyed filler materials Sv1209 and Sv1221 and heat treatment mode on the mechanical properties and structure of welded joints of high-strength aluminum-lithium alloys B-1461 and B-1469 are presented. It is shown that the use of filler materials alloyed with rare earth metals in combination with full heat treatment (quenching and artificial aging) carried out after welding provide an increase in the strength characteristics of the welded joint to the level of strength of the base material with sufficiently high ductility and toughness. Metallographic study of welded joints after heat treatment revealed a fine-grained structure in the center of welds attributed to alloying of the filler with REM. Transmission electron microscopy is used to study precipitated hardening phases in welded joints. The round-shaped phase Al₃(Sc, Zr) and a fine δ’-phase precipitated upon cooling of the welded joint are present in weld adjacent zone of V-1469 alloy. At the same time, artificial aging after welding results in formation of copper-containing Ω’- and θ’-phases. Quenching and artificial aging of the welded joint resulted in an increase in the size of precipitated hardening T₁’-, S’-, θ’-phases and density of their distribution in the grain volume in the heat-affected zone of V-1461 alloy. Thus, heating upon welding leads to uneven phase precipitation, whereas additional artificial aging aggravates the non-uniformity of decomposition through partial dissolution of some phases and coarsening of the other.

1. Kablov E. N., Ospennikova O. G., Vershkov A. V. Rare metals and rare-earth elements — materials of modern and future high tech / Aviats. Mater. Tekhnol. 2013. N S2. P. 3 – 10 [in Russian].

2. Skupov A. A., Ioda E. N., Panteleev M. D. New filler materials for welding of high-strength aluminum-lithium alloys / Tr. VIAM. Élektron. Nauch.-Tekh. Zh. 2016. N 9. Article 04. http://www.viam-works.ru (accessed 30.05.2018) [in Russian].

3. Filatov Yu. A. Research works undertaken at VILS in the field of Al – Mg – Sc wrought alloys. History of development, structure, properties, applications, problems and prospects / Tekhnol. Legk. Splavov. 2017. N 3. P. 7 – 25 [in Russian].

4. Skupov A. A., Panteleev. M. D., Ioda E. N. et al. The efficiency of rare earth metals for filler materials alloying / Aviats. Mater. Tekhnol. 2017. N 3. P. 14 – 19 [in Russian].

5. Mikhaylichenko A. I., Mikhlin E. B., Patrikeev Yu. B. Rare-earth metals. — Moscow: Metallurgiya, 1987. — 232 p. [in Russian].

6. Grushko O. E., Ovsyannikov B. V., Ovchinnikov V. V. Aluminium-lithium alloys: metallurgy, welding, metallography. — Moscow: Nauka, 2014. — 296 p. [in Russian].

7. Makhin I. D., Nikolaev V. V., Petrovichev P. S. Study of weldability of alloys V-1469 and 01570C using electron-beam welding as applied to the advanced manned spacecraft structure / Kosm. Tekhn. Tekhnol. 2014. N 4(7). P. 68 – 75 [in Russian].

8. Ryazantsev V. I. Welded constructions of aluminium-lithium alloys / Aviats. Promyshl. 2005. N 2. P. 32 – 41 [in Russian].

9. Lukin V. I., Skupov A. A., Ioda E. N., et al. Development of filler materials to weld high-strength aluminium-lithium alloys / Vse Mater. Éntsikloped. Sprav. N 7. P. 24 – 30 [in Russian].

10. Kablov E. N., Lukin V. I., Antipov V. V., et al. Efficiency of using filler materials in laser welding of high-strength aluminium-lithium alloys / Svar. Proizv. 2016. N 10. P. 17 – 21 [in Russian].

11. Lukin V. I., Ioda E. N., Panteleev M. D., et al. Heat treatment influence on characteristics of welding joints of high-strength aluminium-lithium alloys / Tr. VIAM. Élektron. Nauch.-Tekh. Zh. 2015. N 4. Article 06. http://www.viam-works.ru (accessed 30.05.2018) [in Russian].

12. Kablov E. N. The strategic direction of development of materials and technologies of their processing for the period till 2030 / Aviats. Mater. Tekhnol. 2012. N S. P. 7 – 17 [in Russian].

13. RF Pat. 2163940. MPK C22 C21/12. Aluminium-based alloy and product made from the same / Fridlyander I. N., Kablov E. N., Kolobnev N. I., Khokhlatova L. B., Samokhvalov S. V., Vorob’ev A. A., Petrakovskii S. A.; applicant and owner All-Russian scientific research institute of aviation materials. — N 99117392; appl. 09.08.1999; publ. 10.03.2001 [in Russian].

14. RF Pat. 2237098. MPK C22 C21/14. Aluminium-based alloy and product made from the same / Fridlyander I. N., Kablov E. N., Grushko O. E., Borovskikh S. N., Ivanova L. A.; applicant and owner All-Russian scientific research institute of aviation materials. — N 20030123027; appl. 24.07.2003; publ. 27.09.2004. Byull. N 6 [in Russian].

15. RF Pat. 2604084. MPK B23 K35/28. Aluminium-based filler material, alloyed with rare-earth metals / Kablov E. N., Lukin V. I., Ioda E. N., Sviridov A. V., Panteleev M. D., Skupov A. A.; applicant and owner All-Russian scientific research institute of aviation materials. — N 2015137405; appl. 02.09.2015; publ. 10.12.2016. Byull. N 34.

16. State Standard GOST 6996–66. Welded joints. Methods for determining mechanical properties. — Moscow: Standsrtinform, 2005. — 44 p. [in Russian].

17. Annin B. D., Fomin V. M., Karpov E. V., et al. Complex research of laser welding of high-strength alloy V-1469 / Aviats. Mater. Tekhnol. 2016. N 3. P. 9 – 16 [in Russian].

18. Alekseev A. A., Lukina E. A., Klochkova Yu. Yu. Crystal structure of ultrathin lamellar precipitates / Fiz. Met. Metalloved. 2013. Vol. 114. N 6. P. 527 – 533 [in Russian].

19. Lukina E. A., Alekseev A. A., Khokhlatova L. B., et al. Regular features of formation of main hardening phases in alloys V-1424 of the Al – Mg – Li – Zn system and V-1461 of the Al – Cu – Li – Zn – Mg system / Metalloved. Term. Obrab. Met. 2013. N 9(699). P. 12 – 17 [in Russian].

20. Kablov E. N., Lukina E. A., Sbitneva S. V., et al. Formation of metastable phases during solid solution decomposition in the process of artificial ageing of aliminium alloys / Tekhnol. Legk. Splavov. 2016. N 3. P. 7 – 17 [in Russian].