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

P. K. Shurkin, Engineer at the Department of Metal Forming, Candidate of Technical Sciences, e-mail: pa.shurkin@yandex.ru
Zh. A. Karpova, Postgraduate Student at the Department of Metal Forming
A. F. Musin, Postgraduate Student at the Department of Metal Forming

Moscow Polytechnic University, Moscow, Russia:

R. A. Latypov, Professor at the Department of Equipment and Technologies of Welding Production

This work is devoted to the study of the structure and properties of welded joints of hot-rolled sheets from the aluminum alloy Al – 4%Zn – 2.5%Mg – 2.5%Ca – 0.2%Zr – 0.1%Sc. The joints were obtained by manual argon-arc method (TIG-welding) using a wire of own production from the base metal composition (sample AlCa) and standard welding wire Of SvAMg5 alloy (sample AlMg). It is shown that in the cast state the alloy structure consists of an aluminum solid solution (Al) (which contains 2.9% Zn, 2.5% Mg, 0.28% Zr and 0.12% Sc) and eutectic crystals of the phase (Al, Zn)₄Ca with a volume fraction of ~7.6%. Microstructural investigation of wrought products showed that the formation of a structure consisting of an aluminum matrix and uniformly distributed spherical particles with a diameter of less than 2 microns occurs as a result of hot rolling with a compression ratio of 95%. The quality of welded joints produced using different additives meets the requirements for the absence of internal defects. The structure in the middle of the joints corresponds to the cast structure of the alloy and has hardness (~80 HV) inferior to the hardness (~105 HV) of the main deformed alloy. Heat-affected zone retains a relatively high hardness (at 95 HV), which is associated with a stabilizing effect of dispersed particles of the eutectic phase (Al, Zn)₄Ca, and also presence of nanoparticles of the phase Al₃(Zr,Sc) in the original sheet. Additional annealing of welds at 350 oC resulted in degradation of the hardness of the AlMg sample to less than 70 HV and relative cross-sectional hardness equalization in the AlCa sample to more than 90 HV. This effect can be explained by the dispersion hardening in case of the AlCa sample due to the separation of coherent nanoparticles of the Al₃(Zr, Sc) phase with the L1₂ structure during the decay of a supersaturated aluminum solid solution. The results of mechanical tests confirmed the advantages of the strength properties of the AlCa sample over the values of the AlMg sample. All samples in the initial state and annealed sample AlMg have strength coefficients relative to the base metal from 72.4 to 75.3. The greatest mechanical properties can be achieved in the welded joint AlCa in the annealed state: UTS = 274±2 MPa, YS = 181±20 MPa, El = 2.9±0.8 %, which corresponds to a coefficient of more than 80%.

This paper was prepared in the framework of the Assignment No. 11.2072.2017/4.6 for implementing a project on the following subject: Developing a process for obtaining deformed semi-finished products made of aluminium-matrix eutectic composites hardened with L1₂ phase nanoparticles with no quenching applied.

1. Drits A. M., Ovchinnikov V. V. Welding of aluminium alloys. Moscow : “Ore and Metals” Publishing House. 2017. 440 p.
2. Oryshenko A. S., Osokin E. P., Barakhtina N. N., Drits A. M., Sosedkov S. M. Aluminum-magnesium alloy 1565 ch (1565ч) for cryogenic application. Tsvetnye Metally. 2012. No. 11. pp. 84–90.
3. Drits A. M., Ovchinnikov V. V., Rastopchin R. N. Study of the properties of the welded joints of 1565ch (1565ч) alloy in connection with the production of the welded tank trucks. Tsvetnye Metally. 2012. No. 12. pp. 85–90.
4. Zykov S. A., Pavlova V. I., Osokin E. P. Mechanical properties of welded joints of the pressed aluminium-magnesium alloy 1565ch at low and high temperatures. Voprosy materialovedeniya. 2018. No. 3. pp. 57–67.
5. Drits A. M., Ovchinnikov V. V., Rastopchin R. N. Processability of sheets made of welded aluminium alloy 1565ch for tanks production. Tekhnologiya legkikh splavov. 2012. No. 3. pp. 20–29.
6. Artsruni A. A., Grigoryan V. A., Drits A. M. Prospects of usage of alloy 1565ch with new approach to aluminium alloys application in armor plating of light fighting machines. Tsvetnye Metally. 2017. No. 5. pp. 80–83.
7. Fengyuan Shu, Ye Tian, Hongyun Zhao, Shaohua Sui, Yuxin Liu et al. Microstructure and mechanical properties of multi-pass TIG welded joint of thick Al – Zn – Mg alloy plate. Materials Research Express. 2019. Vol. 6. p. 1065e1.
8. Wang Dianlong, Diao Guangyun, Liang Zhimin. Comparison of Al – Zn – Mg Alloy P-MIG Welded Joints Filled with Different Wires. High Temperature Materials and Processes. 2019. Vol. 38. pp. 516–524.
9. Toshihiko Fukuda. Weldability of 7000 series aluminium alloy materials. Welding International. 2012. Vol. 26, Iss. 4. pp. 256–269.
10. Hui-Zhong Li, San-Cheng Yao, Xiao-Peng Liang, Yong-Hui, Chen Chao Liu, Lan Huang. Grain boundary pre-precipitation and its contribution to enhancement of corrosion resistance of Al – Zn – Mg alloy. Transactions of Nonferrous Metals Society of China. 2016. Vol. 26, Iss. 10. pp. 2523–2531.
11. Jegdic B. V., Bobic B. M., Pavlovic M. K., Alil A. B., Putic S. S. Stress corrosion cracking resistance of aluminum alloy 7000 series after two-step aging. Chemical Industry and Chemical Engineering Q. 2015. Vol. 21, Iss. 2. pp. 261–268.
12. Shuai Li, Honggang Dong, Lei Shi, Peng Li, Fei Ye. Corrosion behavior and mechanical properties of Al – Zn – Mg aluminum alloy weld. Corrosion Science. 2017. Vol. 123. pp. 243–255.
13. Huang Х., Pan Q., Li B. Effect of minor Sc on microstructure and mechanical properties of Al – Zn – Mg – Zr alloy metal-inert gas welds. Journal of Alloys and Compounds. 2015. Vol. 629, No. 25. pp. 197–207.

14. Ying Deng, Bing Peng, Guofu Xu, Qinglin Pan, Zhimin Yin et al. Effects of Sc and Zr on mechanical property and microstructure of tungsten inert gas and friction stir welded aerospace high strength Al – Zn – Mg alloys. Materials Science and Engineering: A. 2015. Vol. 639. pp. 500–513.
15. Belov N. A. Phase composition of commercial and innovative aluminium alloys. Moscow : MISiS, 2010. 509 p.
16. Belov N. A., Shcherbakov M. V., Belov V. D. On manufacturability of economically alloyed nikalyn AZN0.5F during casting, rolling and welding. Tsvetnye Metally. 2011. No. 12. pp. 94–98.
17. 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, No. 6. pp. 656–666.
18. Belov N. A., Naumova E. A., Akopyan T. K. Effect of calcium on structure, phase composition and hardening of Al – Zn – Mg alloys containing up to 12 wt. % Zn. Materials Research. 2015. Vol. 18, Iss. 6. pp. 1384–1391.
19. Naumova E. A. Use of Calcium in Alloys: From Modifying to Alloying. Russian Journal of Non-Ferrous Metals. 2018. Vol. 59, No. 3. pp. 284–298.
20. Volkova O. V., Dub A. V., Rakoch A. G., Gladkova A. A., Samoshina M. E. Comparison of the Tendency to Pitting Corrosion of Casting of Al6Ca, Al1Fe, and Al6Ca1Fe Experimental Alloys and AK12M2 Industrial Alloy. Russian Journal of Non-Ferrous Metals. 2017. Vol. 58, Iss. 6. pp. 644–648.
21. Alabin A. N., Belov N. A., Tabachkova N. Yu., Akopyan T. K. Heat resistant alloys of Al – Zr – Sc system for electrical applications: Analysis and optimization of phase composition. Non-ferrous Metals. 2015. No. 2. pp. 36–40.
22. Zhichao Guo, Xuan Liu, Jilai Xue. Fabrication of Al – Si – Sc alloy bearing AlSi₂Sc₂ phase using ultrasonically assisted molten salt electrolysis. Journal of Alloys and Compounds. 2019. Vol. 797. pp. 883–889.
23. GOST 2999–75. Metals and alloys. Vickers hardness test by diamond pyramid (incl. Revisions 1, 2). Introduced: 01.07.1976.
24. GOST 1497–84. Metals. Methods of tension test (incl. Revisions 1, 2, 3). Introduced: 01.01.1986.
25. GOST 6996–66 (ISO 4136–89, ISO 5173–81, ISO 5177–81). Welded joints. Methods of mechanical properties determination (incl. Revisions 1, 2, 3, 4). Introduced: 01.01.1967.
26. Huda A. Al-Salihi, Adil Akram Mahmood, Hussain J. Alalkawi. Mechanical and wear behavior of AA7075 aluminum matrix composites reinforced by Al₂O₃ nanoparticles. Nanocomposites. 2019. Vol. 5, Iss. 3. pp. 67–73.
27. Yasuhiro Takashimizu, Maiko Iiyoshi. New parameter of roundness R: circularity corrected by aspect ratio. Progress in Earth and Planetary Science. 2016. Vol. 3, A.N. 2.
28. Mansurov Yu. N., Buravlev I. Yu., Reva V. P., Kurbatkina E. I. Features of structures formation and properties of composite aluminum alloy ingots. Non-Ferrous Metals. 2015. No 2. pp. 40–47.