ML5 alloy structure and properties at different modification methods

A factor exerting a decisive influence on the complex of mechanical, technological and operational properties when making castings of magnesium alloys with a wide crystallization range is the casting structure. It is impossible to obtain a required structure of Mg— Al—Zn alloys without melt modification in the melting process. The paper provides the results obtained when studying the process of ML5 magnesium alloy modification with various substances. The influence of 0,4—0,45 wt.% magnesite introduced in the melt at a temperature of 720—740 °C was studied, as well as the influence of melt purging with oxygen-free carboniferous gases at the same temperature on the structure of the obtained alloy and the time of modification effect retention. The latter is especially important in large-lot and mass production of small Mg—Al—Zn—Mn alloy castings for a long time when melt pouring into molds takes considerable time. It is shown that oxygen-free carboniferous gases used for ML5 alloy modification ensure mechanical properties of castings 15 — 20 % higher than the standard level according to GOST 2856-79. The efficiency of retaining the effect of modification using the standard method (magnesite) and with oxygen-free carboniferous gases is compared. It is shown that the effect of modification with magnesite remains within no more than 30—40 minutes, while the effect of modification with oxygen-free carboniferous gas remains not less than 4 hours that enables long pouring of alloy into molds.

1. Blawert C., Hort N., Kainer K.V Automotive applications of magnesium and its alloys. Trans Indian Inst. Met. 2004. Vol. 57(4). P. 397—408.

2. Garmo E., Black J.T, Kohser R.A. Magnesium and magnesium alloys. In: Materials and processes in manufacturing (8-th ed). USA, Wiley. P. 182—184.

3. Polmear I.J. Magnesium alloys and applications. Mater. Sci. Technol. 1994. Vol. 10. No. 1. P. 1—14.

4. Kulekci M.K. Magnesium and its alloys applications in automotive industry. Inter. J. Adv. Manufactur. Technol. 2008. Vol. 39. No. 9-10. P. 851—865.

5. Chukhrov M.V. Modification of magnesium alloys. Moscow: Metallurgiya, 1972 (In Russ.).

6. Huang Z.H., Guo X.F, Zhang Z.M. Effects of alloying on microstructure and mechanical property of AZ91D magnesium alloy. Rare Met. Mater. Eng. 2006. Vol. 35(3). P. 363—366.

7. Hafllinger U., Hartig C., Hort N., Gtinther R. Modification of magnesium alloys by ceramic particles in gravity die casting. Inter. J. Metal. 2014. Vol. 2014. Article ID 748595.

8. Tang B., Wang Xs., Li S.S., Zeng D.B., Wu R. Effects of Ca combined with Sr additions on micro structure and mechanical properties of AZ91D. Mater. Sci. Technol. 2005. Vol. 21. No. 5. P. 574—578.

9. KoltyginA.V, PlisetskayaI.V. On the behavior of calcium in magnesium casting alloys of Mg—Al—Zn—Mn system. Liteinoeproizvodstvo. 2010. No. 8. P. 2—6 (In Russ.).

10. Belov V.D., Koltygin A.V, Belov N. A., Plisetskaya I.V. Innovations in cast magnesium alloys. Metallurgist. 2010. Vol. 54. No. 5—6. P. 317—321.

11. Fusheng Pan, Mingbo Yang, Xianhua Chen. A Review on casting magnesium alloys: modification of commercial alloys and development of new alloys. J. Mater. Sci. Technol. 2016. Vol. 32. No. 12. P. 1211—1221.

12. Al’tman M.B., Lebedev A.A., Chukhrov M. V Melting and casting of light alloys. Moscow: Metallurgiya, 1969 (In Russ.).

13. Qinglin Jin, Jeong-Pil Eom, Su-Gun Lim, Won-Wook Park, Bong-Sun You. Grain refining mechanism of a carbon addition method in a Mg—Al magnesium alloy. Scripta Mater. 2003. Vol. 49. No. 11. P.1129—1132.

14. Voronov S.M. Selected works on light alloys. Moscow: Oborongiz, 1957 (In Russ.).

15. Lichy P., Cagala M. Microstructure and thermomechanical properties of magnesium alloys castings. Arch. Foundry Eng. 2012. Vol. 12. No. 2. P. 49—54.

16. Sarychikhin N.A., Al’tman N.B., Lebedev A.A., Mukhina I.Yu., Neifak E.V, Goncharov V.B., Tabunov S.A., Chistyakova E.I. Method for producing castings from magnesium-aluminum alloys: Authors certificate. 624701 (SSSR). 1978 (In Russ.).

17. BobryshevB.L, Moiseev V.S., RyakhovskiiA.P., PopkovD.V Method for modifying magnesium alloys of Mg—Al— Zn—Mn system: Pat. 2623965 (RF). 2017 (In Russ.).

18. Fruelling J.W. Protective atmospheres for molten magnesium: Abstr. diss. of PhD. University of Michigan, 1970.

19. Bobryshev B.L. On some aspects of melting of Mg—Zn— Zr alloys. Tekhnologiya mashinostroeniya. 2006. No. 11. P. 5—10 (In Russ.).

20. Bobryshev B.L., Moiseev V.S., Kontorovich I.V. Protection of magnesium alloys from oxidation when filling molds. Tekhnologiya legkikh splavov. 2010. No. 4. P. 49—54 (In Russ.).

21. Velikiy V.I., Yares’ko K.I., Shalomeev V.A., Tsivirko E.I., Vnukov Y.N. Perspective magnesium alloys with elevated level of properties for the aircraft engine industry. Met. Sci. Heat Treatment. 2014. Vol. 55. No. 9-10. P. 492—498.

22. Shalomeev V.A., Lysenko N.A., Tsivirko E.I., Lukinov V.V., Klochikhin V.V. Structure and properties of magnesium alloys with scandium. Metallovedenie i termicheskaya obrabotka metallov. 2008. No. 1. P. 37—40 (In Russ.).