Hereditary effect of the charge structure on Al-Si-Cu alloy density, gas content and solidification processes

The paper provides the results obtained when studying the initial charge structure effect on the density, gas content and temperature-time parameters of AK6M2 (Al-6%Si-2%Cu) alloy solidification. Coarse crystalline charge billets (C-charge) were obtained when pouring the melt into ceramic molds with sand filling providing a cooling rate υ_охл ~0.5÷1.0 °C/s. Finely crystalline charge billets (F-charge) were prepared by pouring the melt to cold cast iron molds (υ_охл ~ 5÷10 °C/s). Charge billets obtained were separately remelted with the same temperature-time conditions, rerefined and degassed with samples taken to determine hydrogen content as well as density values in liquid and solid states. It is established that structural information inherited from the initial charge billets is stable in the solid-liquid-solid system. It was found using direct thermal analysis that the melt obtained from C-charge solidifies with a reduction in liquidus temperature by 3 °С and in the temperatures of the beginning and end of eutectic solidification by 10 °C and 3 °С, respectively, as compared to the melt obtained from C-charge. At the same time, α-Al and eutectic dendrites form in the C-charge melt 0.4 and 0.6 min faster, respectively. The results obtained at the Paraboloid-4 unit showed that the F-charge melt has higher density as compared to the C-charge alloy due to a smaller number of pulses passing through it in the studied temperature range of 750 — 450 °C. Temperature values of aluminum and eutectic dendrite formation determined by J—t temperature relationships (where J is the number of γ pulses, t is the temperature) correlate with the results of direct thermal analysis. General practical recommendations on the purposeful conservation of positive structural information in aluminum alloys are formulated in terms of the structural heredity phenomenon.

1. Nappi C. The global aluminium industry 40 years from 1972. World Aluminium. 2013. http://www.world-aluminium.org/media/filer_public/2013/02/25/an_outlook_of_the_global_aluminium_industry_1972_—_present_day.pdf .

2. Dudin M.N., Voykova N.A., Frolova E.E., Artemieva J.A., Rusakova E.P., Abashidze A.H. Modern trends and challenges of development of global aluminum industry. Metalurgija. 2017. Vol. 56. P. 255—258.

3. Djurdjevic M.B., Odanovic Z., Pavlovic-Krstic J. Melt quality control at aluminum casting plants. Metal. Mater. Eng. 2010. Vol. 16. P. 63—76.

4. McCartney D.G. Grain refining of aluminium and its alloys using inoculants. Inter. Mater. Rev. 1989. Vol. 34. No. 5. P. 247—260.

5. Murty B.S., Kori S.A., Chakraborty M. Grain refinement of aluminium and its alloys by heterogeneous nucleation and alloying. Inter. Mater. Rev. 2002. Vol. 47. No. 1. P. 3—29.

6. Nikitin V.I., Nikitin K.V. Heredity in cast alloys. Moscow: Mashinostroenie-1, 2005 (In Russ.).

7. Nikitin K.V., Nikitin V.I., Timoshkin I.Yu. Quality control of cast products from aluminium alloys based on the phenomenon of structural heredity. Moscow: Radynitsa, 2015 (In Russ.).

8. Selyanin I.F., Deev V.B., Kukharenko A.V. Resource-saving and environment-saving production technologies of secondary aluminum alloys. Russ. J. Non-Ferr. Met. 2015. Vol. 56. No. 3. P. 272—276.

9. Deev V.B. Fabrication of sealed aluminum alloys from recycled materials. Moscow: Flinta-Nayka, 2006 (In Russ.).

10. Sigworth G.K. The modification of Al—Si casting alloys: Important practical and theoretical aspects. Inter. J. Metalcast. 2008. Vol. 2. No. 2. Р. 19—40.

11. Rathod N.R., Manghani J.V. Effect of modifier and grain refiner on cast Al—7Si aluminum alloy: A review. Inter. J. Emerging Trends in Engineering and Development. 2012. Vol. 5. No. 2. Р. 574—581.

12. Faraji M., Katgerman L. Grain refinement and modification in hypoeutectic Al—Si alloys. Foundry Trade J. 2010. Vol. 184. P. 315—318.

13. Fang Q., Granger D. Porosity formation in modified and unmodified A356 alloy castings. AFS Trans. 1989. No. 97. P. 989—1000.

14. Zhang J., Chen H., Yu H., Jin Y. Study on dual modification of Al—17%Si alloys by structural heredity. Metals. 2015. No. 5. Р. 1112—1126.

15. Xu H., Jiana X., Meek T., Han Q. Degassing of molten aluminum A356 alloy using ultrasonic vibration. Mater. Lett. 2004. Vol. 58. P. 3669—3673.

16. Jian X. Meek T.T., Han Q. Refinement of eutectic silicon phase of aluminum A356 alloy using high-intensity ultrasonic vibration. Scripta Mater. 2006. Vol. 54. No. 5. P. 893—896.

17. Mizutani Y., Miwa K., Yasue K., Tamura T., Sakaguchi Y., Ohura Y. Effect of the electromagnetic vibration intensity on microstructural refinement of Al—7%Si alloy. Mater. Trans. 2004. Vol. 45. Nc. 6. P 1944—1948.

18. Mizutani Y., Miwa K., Yasue K., Tamura T., Sakaguchi Y., Kawai S. Effect of the intensity and frequency of electromagnetic vibrations on refinement of primary silicon in Al—17%Si alloy. Mater. Trans. 2004. Vol. 45. No. 6. P. 1939—1943.

19. Donii O., Narizhna T., Voron M., Berest D. Influence of the external Magnetic field on the structure and properties of the hypereutectic aluminum-silicon alloy. Mater. Sci. Non-Equilibr. Phase Trans. 2018. Vol. 4. No. 3. P. 79—82.

20. Brodova I.G., Popel P.S., Eskin G.I. Liquid metal processing: application to aluminium alloy production. N.Y.—London: Gordon&Breach, 2004.

21. Quested P., Morrell R., Dinsdale A., Chapman L. The measurement and estimation of density for selected liquid alloys. In: Proc. of the 6-th Decennial Inter. Conf. on Solidification Processing (Beaumont Estate, Old Windsor, UK, 25—28 July 2017). Liquid Metal Engineering Hub. 2017. Р. 1—5.

22. Nikitin K.V., Finkel'shtein A.B., Chikova O.A., Timoshkin I.Yu. Influence of the structure of the AlSi20 foundry alloy on the microstructure and viscosity of the Al—6% Si model silumin in solid and liquid states. Russ. J. Non Ferr. Met. 2013. Vol. 54. No. 4. Р. 314—319.

23. Nikitin K.V., Nikitin V.I., Timoshkin I.Yu., Krivopalov D.S., Chernikov D. Hereditary influence of the structure of charge materials on the density of aluminum alloys of the Al—Si system. Russ. J. Non-Ferr. Met. 2015. Vol. 56. No. 1. Р. 20—25.

24. Nikitin K.V., Nikitin V.I., Timoshkin I.Yu., Krivopalov D.S., Chernikov D.G. Influence of the structure of charge billets, overheating,and holding time of melts on the properties of Al—5 wt % Cu alloys in liquid and solid states. Russ. J. Non-Ferr. Met. 2015. Vol. 56. No. 2. Р. 165— 170.

25. Ri E.H., Ri Hosen, Dorofeev S.V., Yakimov V.I. Influence of irradiation of liquid phase by nanosecond electromagnetic pulses on its structure, crystallization processes, structure formation and properties of casting alloys. Vladivostok: Dal'nauka, 2008 (In Russ.).

26. Girshovich N.G., Nekhendzi Yu.A. Solidification of castings In: Solidification of metals: Proc. 2-nd Century on the theory of casting processes. Moscow: Mashgiz, 1958. Р. 39—90 (In Russ.).