Quaternary Mg-2at.%Zn-3at.%Ca-X (X = 0.3at.%La, 0.2at.%Nd, 0.3at.%Y, 0.2at.%Zr) alloys were prepared by melt spinning. Thermal stability of the ribbons has been studied step-by-step after isochronal and isothermal annealing by microhardness measurements, XRD analysis and microstructure observations. The alloys solidifi ed as a three-phase mixture – Mg solid solution, Mg2Ca and Mg6Ca2Zn3. At least three age hardening phenomena have been observed. The most pronounced age
hardening effects occurred after heating for 1hour at temperature of 225 oC. This effect corresponds to Mg solid solution decomposition and fi ne precipitate formation. Apparent activation energy of this phenomenon equals to 64-71 kJ/mol. Further microhardness changes associated with annealing are caused by changes in the quantity, shape and size of the particles. In respect of optimal high strength and heat resistance Nd addition has appeared to be the most effective.
REFERENCES
1. Hehmann F., Jones H., in: T.S.Srivatsan, T.S.Sudarshan (Eds.), Rapid Solidifi cation
Technology, 441, (1993).
2. Park W. W., You B. S., Jardim P. M., Vander Sande J. B., Solorzano I. G., in: E. Aghion
and D. Eliezer (Eds.) Proceeding of the 2nd Israel International Conference of Magnesium Scienc. & Technology, Israel, 2000, p. 198–210.
3. You B. S., Park W. W. and Chung I. S., Scripta mater. 42, (2000) p. 1089–1094.
4. Yim C. D., Kim Y. M., You B. S., Materials Transactions, 48, 5 (2007) p. 1023–1027.
5. Bamberger M., Levi G., and Vander Sande J. „Precipitation Hardening in Mg-Ca-Zn
Alloys,” Metallurgical and Materials Transactions A, 37 (2006), p. 481-487.
6. Larionova T., Park W.-W., You B.-S. Scripta Materialia, 45 (2001) p. 7-13.
7. Hantzsche K., Bohlen J., Wendt , Kainer K. U., Yi S.B., Letzig D. Scripta Materialia, 63,
7, (2010), p. 725–730.
8. Hono K., Mendis C. L., Sasaki T. T., Oh-ishi K. Scripta Materialia, 63, 7, (2010) p. 710–715.
9. Langelier B., Esmaeili S. Proc. Symp. Magnesium Technology, TMS (2010).
10. Vasilyev А. А., Kuzmin N. L., Gruzdev A. S. FTT, 53, 8 (2011) p. 1576–1581.
11. Watanabe H., Abe N., Sato E. Bulletin of Chiba Institute of Technology, 19, (1975)
p. 44–49.
12. Rokhlin L.L. Tarytina I.Ye. Phys.Met.Metall., 59, 6 (1985) p. 136–141.
13. Omori G., Matsuo S., Asada M. Journal of Japan Insitute of Metals, 36, 10 (1972)
p. 1002–1008.
