Influence of Technology of Hot Forming of Plates from Aluminum Alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu on Resistance to Fatigue Fracture

OBRABOTKAMETALLOV Vol. 22 No. 4 2020 107 MATERIAL SCIENCE In fl uence of Technology of Hot Forming of Plates from Aluminum Alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu on Resistance to Fatigue Fracture Kirill Zakharchenko 1, 2, a, * , Vladimir Kapustin 2, 1, b , Alexey Larichkin 1, 3, c , Yaroslav Lukyanov 1, d 1 Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences, 15 Akademika Lavrentieva Prospekt, Novosibirsk, 630090, Russian Federation 2 Novosibirsk State Technical University, 20 Prospekt K. Marksa, Novosibirsk, 630073, Russian Federation 3 Novosibirsk State University, 1 Pirogova Str., Novosibirsk, 630090, Russian Federation a https://orcid.org/0000-0003-2626-6184, zaharchenkok@mail.ru , b https://orcid.org/0000-0001-6124-2503, macler06@mail.ru , c https://orcid.org/0000-0002-7306-9522, larichking@gmail.com, d https://orcid.org/0000-0003-4526-9399, lukyanov@hydro.nsc.ru Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2020 vol. 22 no. 4 pp. 94–109 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2020-22.4-94-109 Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov ARTICLE INFO Article history : Received: 11 August 2020 Revised: 26 August 2020 Accepted: 14 September 2020 Available online: 15 December 2020 Keywords : Aluminum-lithium alloy Elastoplastic strain Strain characteristics Creep Shaping Structure Accelerated method to evaluate metal fatigue resistance Finite element method Funding The reported study was funded by RFBR and Novosibirsk region according to the research project № 19-48-543028. Acknowledgements The authors express their gratitude to the leading process engineer of the branch of PJSC “Company “Sukhoi” “VP Chkalov Novosibirsk Aircraft Plant”, Ph.D. (Engineering) Galina Rae- vskaya for consultations in the work. ABSTRACT Introduction. One of the primary objectives in the development of promising aircraft products is to reduce the weight of the aircraft structure. This problem can be solved by applying new low density materials such as aluminum alloys alloyed with lithium (for example, Al-Cu-Li-Zn) in the design of parts. The use of these materials in aircraft construction is limited by the processing technology, which must be such as not to damage the material and not reduce its strength properties. Such technologies include processing by pressure with heating, when creep processes are activated and the material passes into a state close to superplasticity. The purpose of the work: assessment of the effect of pressure shaping of aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu in creep mode on strength. The paper investigates the in fl uence of the technology of pressure shaping of aluminum alloys Al-Cu-Li-Zn andAl-Zn-Mg-Cu on the resistance to fatigue failure. The work uses a method that allows to determine the ultimate stresses using diagrams of the accumulation of irreversible deformations; method of forming thick plates (40 mm) in the creep mode. The previously selected optimum temperatures for forming the plates are used. A non-contact coordinate measuring system is used to perform surface inspection after shaping. Fractography of the fracture of samples of alloy Al-Cu-Li-Zn and Al-Zn- Mg-Cu after fatigue failure is performed. Mathematical modeling of the deformation process of plates in creep mode is carried out in the MSC.Marc package. As a result , a conservative evaluation of the endurance limit for aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu is obtained. The shaping of thick plates in the creep mode is carried out. More than 80% of the board surface is formed with a deviation of less than 1 mm from the target size. Fatigue tests of samples made of molded panels of alloys Al-Cu-Li-Zn and Al-Zn-Mg- Cu are carried out, fatigue curves are plotted. The fractography of the surface of the fatigue fracture showed the presence of oxides in the samples of alloy Al-Cu-Li-Zn, in contrast to alloy Al-Zn-Mg-Cu. The results of fatigue tests are discussed , showing that the characteristics of the technological process of shaping and heat treatment do not deteriorate the fatigue properties of the investigated alloys. Comparative tests show that alloy Al-Cu-Li-Zn has higher fatigue characteristics. Mathematical modeling show that the use of the Boyle- Norton steady-state creep law is not enough to describe the process of plate forming. The necessity of setting the inverse problem of creep age forming is noted, where the coordinates of the punches of the loading device should act as boundary conditions. For citation: Zakharchenko K.V., Kapustin V.I., Larichkin A.Yu., Lukyanov Ya.L. In fl uence of technology of hot forming of plates from aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu on resistance to fatigue fracture. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science , 2020, vol. 22, no. 4, pp. 94–109. DOI: 10.17212/1994-6309-2020-22.4-94-109. (In Russian). ______ * Corresponding author Zakharchenko Kirill V. , Ph.D. (Engineering), Senior Lecturer Novosibirsk State Technical University, 20 Prospekt K. Marksa, 630073, Novosibirsk, Russian Federation Tel.: +7 (383) 346-17-64, e-mail: zaharchenkok@mail.ru