STUDY INTO THE INFLUENCE OF THE GRAIN STRUCTURE REFINEMENT DEGREE OF ALLOY 6063 INGOTS ON THEIR PLASTICITY, EXTRUSION PARAMETERS AND PROPERTIES OF EXTRUDED PROFILES

The analysis of scientific and technical literature and practical data made it possible to found that changes in casting parameters for ingots using different mold designs allows varying the degree of ingot grain structure refinement in a sufficiently wide range, which should be reflected in the conditions of aluminum alloy profile extrusion as well as physical and mechanical properties of these profiles. Therefore, the purpose of the research was to assess the influence of the degree of grain structure refinement for Alloy 6063 ingots on extrusion deformation and speed parameters and mechanical properties of profiles produced. The study used several batches of Alloy 6063 ingots 178 mm in diameter cast under industrial conditions, as well as profiles obtained by direct extrusion on a 18 MN horizontal hydraulic press subjected to quenching and aging. The grain size in homogenized ingots was estimated by light microscopy using the Olimpus optical microscope, and mechanical properties tests were carried out using the Inspect 20 kN-1 universal test machine. It was found that the initial grain size in the ingot structure exerts a significant influence both on ingot plasticity during extrusion, and on the final structure and mechanical properties of profile products made of aluminum alloys. Having analyzed the results obtained, we can conclude that the increase in strength characteristics of products extruded from ingots with a more refined structure is due to the fact that fine grains are retained in the structure of metal after its deformation, and cast metal plasticity increases with the degree of grain structure refinement in the ingot. This leads to the higher efficiency of profile product hardening and metal outflow rate during extrusion.

grain size, casting, extrusion, mechanical properties, structure

1. Makarov G.S. Ingots from aluminum alloys with magnesium and silicon for pressing. Basics of production. Мoscow: Intermet Engineering, 2011 (In Russ.).

2. Saha P.K. Aluminum extrusion technology. Moscow: APRAL, 2015 (In Russ.).

3. Grishchenko N.A., Sidelnikov S.B., Gubanov I.Yu., Lopatina E.S., Galiev R.I. Mechanical properties of aluminum alloys. Krasnoyarsk: SibFU, 2012 (In Russ.).

4. Yu Z.H., Zhang D.T., Zhang W., Qiu C. Deformation be- havior and microstructure evolution of 6063 alloy during hot compression. Mater. Sci. Forum. 2018. Vol. 913. P. 63—68.

5. Kaibyshev O.A., Valiev R.Z. Boundaries of grains and the properties of metals. Moscow: Metallurgiya, 1987 (In Russ.).

6. Ovsyannikov B.V. Careful — grain modification. Tekh- nologiya legkikh splavov. 2015. No. 2. P. 40—45 (In Russ.).

7. Donik C. Influence of artificial aging on the electroche- mical properties of the aluminium AA 6063 alloy. Mater. Tehnol. 2018. Vol. 52(1). P. 71—75.

8. Khlif M., Aydi L., Nouri H., Bradai C. High strain-rate tensile behaviour of aluminium A6063. In: Proc. 7-th Conf. on Design and Modeling of Mechanical Systems (CMSM’2017) (March 27—29, Hammamet, Tunisia). Lecture Notes Mech. Eng., 2018. P. 865—870.

9. Kubásek J., Vojtěch D., Dvorskỳ D. Structure and mechanical properties of aluminium alloy sampled from a firefighter ladder. Manufact. Technol. 2017. Vol. 17(6). P. 876—881.

10. Abioye O.P., Abioye A.A., Atanda P.O., Osinkolu G.A., Folayan A.J. Numerical simulation of outer die angle of equal channel angular extrusion process. Int. J. Mech. Eng. Technol. 2017. Vol. 8(12). P. 264—273.

11. Wang Y., Zhao S., Zhao X. Microstructure of semi-solid 6063 alloy fabricated by radial forging combined with unidirectional compression recrystallization and partial melting process. MATEC Web of Conferences. 2017. No. 136. 01003.

12. Wang Y.Q., Yuan H.X., Chang T., Du X.X., Yu M. Compressive buckling strength of extruded aluminium alloy I-section columns with fixed-pinned end conditions. Thin- Walled Structures. 2017. Vol. 119. P. 396—403.

13. Wang Y., Zhao S., Zhang C. Microstructural evolution of semisolid 6063 aluminum alloy prepared by recrystallization and partial melting process. J. Mater. Eng. Performa. 2017. Vol. 26(9). P. 4354—4363.

14. Li S.-K., Li L.-X., Liu Z.-W., Wang G. Effect of extrusion speed on weld strength of 6063 square tube. Zhongguo Youse Jinshu Xuebao. Chin. J. Nonferr. Met. 2017. Vol. 27(9). P. 1775—1784.

15. Liu Z.-W., Li L.-X., Yi J., Li S.-K., Wang Z.-H., Wang G. Influence of heat treatment conditions on bending characteristics of 6063 aluminum alloy sheets. Trans. Nonferr. Met. Soc. China (Eng. Ed.). 2017. Vol. 27(7). P. 1498—1506.

16. Imam M., Racherla V., Biswas K., Fujii H., Chintapenta V., Sun Y., Morisada Y. Microstructure-property relation and evolution in friction stir welding of naturally aged 6063 aluminium alloy. Int. J. Adv. Manufact. Technol. 2017. Vol. 91(5-8). P. 1753—1769.

17. Muhammad W., Brahme A.P., Kang J., Mishra R.K., Inal K. Experimental and numerical investigation of texture evolution and the effects of intragranular backstresses in aluminum alloys subjected to large strain cyclic deformation. Int. J. Plastic. 2017. Vol. 93. P. 137—163.

18. Al-Marahleh G. Effect of heat treatment parameters on distribution and volume fraction of Mg2Si in the structural Al 6063 alloy. Amer. J. Appl. Sci. 2006. Vol. 3 (5). P. 1819—1823.

19. Bryantsev P.Y. Research and optimization of modes of thermal processing of ingots of alloys of system Al—Mg— Si: Abstr. diss. of PhD. Moscow: MISIS, 2007 (In Russ.).

20. Gorelik S.S. Recrystallization of metals and alloys. 2-nd ed. Мoscow: Metallurgiya, 1978 (In Russ.).

21. Bandini C., Reggiani B., Donati L., Tomesani L. Development and validation of a dynamic and static re crystallization model for microstructural prediction of AA6060 aluminum alloy with qform. In: Proc. Conf. Eleventh International Aluminum Extrusion Technology Seminar. Madison: Omnipress, 2016. Vol. 1. P. 789—800.