National University of Science and Technology MISiS, Moscow, Russia:

A. V. Koltygin, Assistant Professor of a Chair of Casting Technologies and Art Material Processing
V. E. Bazhenov, Assistant Professor of a Chair of Casting Technologies and Art Material Processing, e-mail: V.E.Bagenov@gmail.com

The ML10 (NZ30K) magnesium alloy is usually melted from MZr1N3 (bal. Mg, 1wt.% Zr, 3wt.% Nd) by adding Mg – 15wt.%Zr (L2 or L4), Mg –20wt.%Nd (МN) master alloys and pure zinc. Solikamsk Experimental Magnesium Plant was the first manufacturer of magnesium alloys that offered the ML10 alloy ingots on the Russian market. Two samples of the ML10 alloy, manufactured by Solikamsk Experimental Magnesium Plant, were investigated. Alloy ingots come in rectangular and cylindrical shapes. The alloy microstructure is typical for the as-cast ML10 alloy. However, in the sample that was cut off from the ingots edge, the level of zinc and neodymium was maximal, whilst the level of zirconium was minimal. On the other hand, the level of zinc and neodymium was minimal in the samples that were cut off from the center of the ingots, whilst zirconium level was maximal. Furthermore, the level of neodymium in the center of the ingot was below the standard limit. Furthermore, a segregation of ingot components must be considered during the alloy preparation. A cylindrical ingot was melted and bars were cast and heat treated. The bars were heat treated according to T4 (solution-treated at 530–540 °C for 8 hours) and T6 temper (solution-treated at 530–540 °C for 8 hours, air cooled, and then aged at 200 °C for 8 hours). The mechanical properties were determined, using cylindrical samples, machined from the bars with 10 mm diameter. ML10-T6 alloy has the tensile strength σ_в = 232±16 MPa, yield strength σ_0,2 = 151±15 MPa, and elongation δ = 6.8±1.8%. Hardness of the ML10-T6 and ML10 T4 alloys is 68 HB and 57 HB, respectively. The ML10-T6 alloy fractures were investigated. The fracture is typical for the ML10 alloy. The fracture does not contain non-metallic inclusions, which means that the alloy is pure. The loss of alloying elements from the melt during the melting process was determined. In case of a 3-hour holding of the ML10 alloy in the steel crucible under a protective flux cover and at the temperature of 760–780 °C, the levels of neodymium and zirconium were reduced by 0.3% and 0.22%, respectively. The level of zinc did not change during the holding. The investigated alloys are recommended as raw materials for producing castings of the ML10 alloy in a production environment.

1. Zheng X. W., Dong J., Liu W., Ding W. J. Microstructure and mechanical properties of NZ30K alloy by semicontinuous direct chill and sand mould casting processes. China foundry. 2011. Vol. 8, No. 1. pp. 41–46.
2. Nie J.-F. Precipitation and hardening in magnesium alloys. Metallurgical and Materials Transactions: A. 2012. Vol. 43, No. 11. pp. 3891–3939.
3. Altman M. B., Antipova A. P., Blokhina V. A., Blyablin A. A. Magnesium alloys: reference book. Part 1. Metal science of magnesium and its alloys. Fields of application. Moscow : Metallurgiya, 1978. 232 p.
4. Penghuai F., Liming P., Haiyan J., Lan M., Chunquan Z. Chemical composition optimization of gravity cast Mg – yNd – xZn – Zr alloy. Materials Science and Engineering A. 2008. Vol. 496. pp. 177–188.
5. Yang W., Liu L., Zhang J., Ji S., Fan Z. Heterogeneous nucleation in Mg – Zr alloy under die casting condition. Materials Letters. 2015. Vol. 160. pp. 263–267.
6. Mukhina I. Yu., Lebedev V. M., Kim K.-H., Kim D.-K. Investigation of the microstructure and properties of a stable neodymium- and yttrium-bearing magnesium alloys at elevated temperatures. Metal Science and Heat Treatment. 1997. Vol. 39, No. 5/6. pp. 202–206.
7. Altman M. B., Belov A. F., Dobatkin V. I. et al. Magnesium alloys: reference book. Part 2. Moscow : Metallurgiya, 1978. 294 p.
8. Tikhonova N. M., Blokhina V. A., Antipova A. P. Heat resistant magnesium alloys. The book: Magnesium alloys. Moscow : Nauka, 1978. pp. 58–62.
9. RTM 1.4.1772–87. Specialized technological equipment. Ressorts.
10. Uridiya Z. P., Mukhina I. Yu., Duyunova V. A., Kozlov I. A. The origins of flux corrosion in mouldings made of heatproof cast magnesium alloy ML10. Trudy VIAM. 2016. No. 12. DOI: 10.18577/2307-6046-2016-0-12-2-2
11. Uridiya Z. P., Mukhina I. Yu., Frolov A. V., Leonov A. A. Study of microstructure of magnesium-zirconium master alloy and heat-resistant magnesium alloy ML10. Trudy VIAM. 2015. No. 10. DOI: 10.18577/2307-6046-2015-0-10-6-6
12. State Standard GOST 1583—93. Aluminium casting alloys. Specifications. Introduced: 1997–01–01.
13. State Standard GOST 2856—79. Casting magnesium alloys. Grades. Introduced: 1981–01–01.
14. Koltygin A. V. Analysis of Possible Phase Transformations in Crystallization and their Effect on Cast Structure in Alloy ML10. MiTOM. 2013. No. 8. pp. 25–28.
15. Gorsse S., Hutchinson C. R., Chevalier B., Nie J.-F. A thermodynamic assessment of the Mg – Nd binary system using random solution and associate models for the liquid phase. Journal of Alloys and Compounds. 2005. Vol. 392. pp. 253–262.
16. Yu K., Li W.-X., Wang R.-C. Mechanical properties and microstructure of as-cast and extruded Mg – (Ce, Nd) – Zn – Zr alloys. Journal of Central South University of Technology. 2005. Vol. 12, No. 5. pp. 499–502.
17. Feng H., Liu H., Cao H., Yang Y., Xu Y., Guan J. Effect of precipitates on mechanical and damping properties of Mg – Zn – Y – Nd alloys. Materials Science and Engineering: A. 2015. Vol. 639. pp. 1–7.
18. Bettles C. J., Gibson M. A., Zhu S. M. Microstructure and mechanical behaviour of an elevated temperature Mg-rare earth based alloy. Materials Science and Engineering: A. 2009. Vol. 505. pp. 6–12.