South Ural State University, Chelyabinsk, Russia:

S. V. Rushchits, Professor of the Department of Material Science and Physics and Chemistry of Materials
A. M. Akhmedyanov, Head of the Physical Simulation of Thermomechanical Processing Laboratory

JSC Arconic SMZ, Moscow, Russia:
A. M. Drits, Director for Business Development and New Technologies, e-mail: Alexander.Drits@arconic.com
V. N. Nuzhdin, Manager for New Technologies

The paper presents results of physical modelling of the process of hot deformation of casted and homogenized 1565ch aluminum alloy with chemical composition: Al – 5.4% Mg – 0.80% Mn – 0.68% Zn – 0.17% Fe – 0.12% Si – 0.09% Cr – 0.09% Zr (wt.%). Hot deformation by uniaxial compression of cylindrical samples in the temperature range of 350–500 ^oС and strain rates in the range of 0.001–10 s^–1 were carried out on thermomechanical simulator Gleeble 3800. The indicated ranges of temperature and strain rate contain the ranges that can be regarded as typical for the extrusion process of the alloy under consideration. The horizontal plateaus on the obtained flow stress curves bear evidence of dynamical recovery processes running during the deformation. The steady-state stresses rise with the increase of strain rate and the decrease of deformation temperature. It is clarified that the steady-state stresses in the alloy with casted and homogenized structure appear to be somewhat lower than in the alloy having structure that was preliminarily hot-deformed (e.g. by rolling). However, this difference is not so tangible, as it doesn’t exceed 7%. In the region of intermediate values of module-compensated steady-state stresses (1.5·10^–3 < σ_s/G < 4.7·10^–3) the strain rate is directly connected with the stress by the exponential law with the energy of activation Q = 138.3 kJ/mol and the exponent n = 4.3. The obtained estimates of the parameters of the power law show that the process that limits the rate of hot deformation in the region of intermediate stresses is the diffusion-controlled motion of dislocations. The index of strain rate sensitivity m takes on a value of 0.23, which is the necessary condition of the alloy’s high ductility under tensile tests. In the region of high values of the steady-state stresses we observed sudden drop in index of strain rate sensitivity — this is accounted for the alteration of the deformation processes that determine the strain rate. The decrease of the strain rate sensitivity in the region of low values of the steady-state stresses is explained by the approach of the stress values to the threshold level, required for breakaway of dislocations from incoherent inclusions present in the alloy. An empirical expression has been obtained, that can be used for the prediction of steady-state stress values in accordance with given thermal and strain rate parameters of the deformation. A deformation map of the 1565ch alloy has been plotted; it can be used as a tool for selection of the optimal operating conditions for the extrusion process.

1. Oryshchenko A. S., Osokin E. P., Barakhtina N. N., Drits A. M., Sosedkov S. M. Aluminum-magnesium alloy 1565ch for cryogenic application. Tsvetnye Metally. 2012. No. 11. pp. 84–90.
2. Drits A. M., Ovchinnikov V. V., Rastopchin R. N. Technological properties of weldable 1565ch aluminium alloy sheets used for production of transportation tanks. Tekhnologiya legkikh splavov. 2012. Vol. 3. pp. 20–29.
3. Drits A. M., Nuzhdin V. N., Preobrazhenskiy E. V., Eremeev N. V. Optimization of mechanical properties and hardness of cold-worked plates out of 1565ch aluminium alloy. Tsvetnye Metally. 2017. No. 1. pp. 26–29.
4. Rushchits S. V., Aryshensky E. V., Sosedkov S. M., Akhmedyanov A. M. Modeling the hot deformation behavior of 1565ch aluminum alloy. Key engineering materials. 2016. Vol. 684. pp. 35–41.
5. Rushchits S., Aryshenskii E., Kawalla R., Serebryany V. Investigation of texture structure and mechanical properties evolution during hot deformation of 1565 aluminum alloy. Materials science forum. 2016. Vol. 854. pp. 73–78.
6. Yang D., Quan Y., Zhao H., Zhang Z., Huang G., Liu Q. Effects of deformation heating on constitutive analysis of a new Al – Mg – Si – Cu alloy during hot compression. Materials science forum. 2014. Vol. 794–796. pp. 1263–1268.
7. Blum W., Zhu Q., Merkel R., McQueen H. J. Geometric dynamic recrystallization in hot torsion of Al – 5Mg – 0.6Mn (AA5083). Materials science and engineering: A. 1996. Vol. 205. pp. 23–33.
8. Kassner M., Perez-Prado M.-T. Fundamentals of creep in metals and alloys. Amsterdam : Elsevier, 2004. 288 p.
9. Yavari P., Mohamed F. A., Langdon T. G. Creep and substructure formation in an Al – 5% Mg solid solution alloy. Acta metallurgica. 1981. Vol. 29. pp. 1495–1502.
10. Rothman S. J., Peterson N. L., Nowicki L. J., Robinson L. C. Tracer diffusion of magnesium in aluminum single crystals. Physica status solidi (b). 1974. Vol. 63. pp. K29–K33.
11. Robinson S. L., Sherby O. D. Activation energy for lattice self-diffusion. Physica status solidi (a). 1970. Vol. 1. pp. K119–K122.
12. Horiuchi R., Otsuka M. Mechanism of the high temperature creep of aluminum-magnesium alloys. Transactions of the Japan Institute of Metals. 1972. Vol. 13. pp. 284–293.
13. Nakashima H., Iwasaki K., Goto S., Yoshinaga Y. Combined effect of solution and dispersion hardening at high temperature. Materials transaction, JIM. 1990. Vol. 31, No. 1. pp. 35–45.
14. Taleff E. M., Henshall G. A., Nien T. G., Lesuer D. R., Wadsworth J. Warm-temperature tensile ductility in Al – Mg alloys. Metallurgical and materials transactions: A. 1998. Vol. 29A. pp. 1081–1091.
15. Sherby O. D., Taleff E. M. Influence of grain size, solute atom and secondphase particles on creep behavior of polycrystalline solids. Materials science and engineering: A. 2002. Vol. 322. pp. 89–99.
16. Siethoff H., Ahlborn K. Steady-state deformation of solid solution alloys at high stress. Physica status solidi (a). 1991. Vol. 128. pp. 397–406.
17. Frost H. J., Ashby M. F. Deformation-mechanism maps: the plasticity and creep of metals and ceramics. New York : Pergamon Press, 1982. 166 p.
18. Garofalo F. An empirical relation defining the stress dependence of minimum creep rate in metals. Transactions of the Metallurgical Society of AIME 227. 1963. pp. 351–356.
19. Sellars M., Tegart W. J. McG. Hot workability. International materials reviews. 1972. Vol. 17. pp. 1–24.
20. Hart E. Theory of the tensile test. Acta metallurgica. 1967. Vol. 15. pp. 351–355.
21. Hutchinson J., Neale K. Influence of strain-rate sensitivity on necking under uniaxial tension. Acta metallurgica. 1977. Vol. 25. pp. 839–846.
22. Taleff E. M., Lesuer D., Wadsworth J. Enhanced ductility in coarsegrained Al – Mg alloys. Metallurgical and materials transaction: A. 1996. Vol. 27A. pp. 343–352.
23. Taleff E. M., Nevland P. J. The high-temperature deformation and tensile ductility of Al alloys. JOM. January 1999. pp. 36–38.
24. Taleff E. M., Nevland P. J., Krajewski P. E. Tensile ductility of several commercial aluminum alloys at elevated temperatures. Metallurgical and materials transactions: A. 2001. Vol. 32A. pp. 1119–1130.
25. Taleff E. M., Takata K., Ichitani K. Hot and warm deformation of AA5182 sheet materials: ductility and microstructure evolution. Proceedings of the 12^th International Conference on 1231 Aluminium Alloys. Yokohama, Japan, September 5–9, 2010. pp. 1231–1236.