Grain Refining Behavior of Zr, Al₂Y and Al₄C₃ Particles in Magnesium Alloys by the First-Principles Calculations

Abstract:

Grain refining is one of the most important issues in the applications of Mg alloys, which directly determines mechanical properties and deformability. Therefore the understanding of grain refining mechanism during solidification will be benefit to develop new grain refiners. Herein refining role was elucidated by the first principles calculations based on adsorption behavior of a Mg atom on the closest-packed planes of grain refiners (Zr (001), Al₂Y(311) and Al₄C₃(102)). Taking into account different sites, the site with the maximum adsorption energy value generally corresponded to the most possible location. The adsorption energy results show that the possible refining turn follows Al₄C₃(102)>Zr (001)>Al₂Y(311). Meanwhile, the structural optimization confirmed that the Mg atom connected with two C atoms on the top of zig-zag plane of Al₄C₃(102), three Zr atoms at the hcp position on Zr (001), and two Y atoms and one Al atom at the bottom of zig-zag plane of Al₂Y(311). The density of states revealed that the variation of d-orbital electrons of Mg atom became apparent during adsorption process. The values of Mulliken charges were 0.898 e in Al₄C₃(102), 0.410 e in Zr (001) and 0.245 e in Al₂Y(311), respectively. This tendency agrees well with the previous experimental results. It indicates the adsorption energy on the closest-packed planes can be regarded as a prerequisite to select new grain refiners for Mg alloys in future.

• Periodical: Materials Science Forum (Volume 816)
• Pages: 370-374
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.816.370
• Online since: April 2015
• Authors: Jun Ling Pan, Qiu Ming Peng, Jian Xin Guo, Hui Li
• Keywords: First-Principles Calculations, Grain Refiner, Mg Alloys

References

[1] C. Potzies, K. U. Kainer, Fatigue of Magnesium Alloys, Adv. Eng. Mater. 6(2004) 281-289.

DOI: 10.1002/adem.200400021

[2] S. Schumann, The paths and strategies for increased magnesium applications in vehicles, Mater. Sci. Forum. 1(2005) 488-489.

DOI: 10.4028/www.scientific.net/msf.488-489.1

[3] K. Achenbach, H. Nipper, E. Piwowarsky, Contribution to the question of melting practice for cast magnesium alloys Die Giesserei. 26(1939) 621-623.

[4] E. F. Emley, Priciples of magnesium technology (Oxford: Pergamon Press 1966).

[5] Y. Lee, A. Dahle, D. StJohn, The role of solute in grain refinement of magnesium, Metall. Mater. Trans A. 31(2000) 2895-2906.

DOI: 10.1007/bf02830349

[6] M. Qian, D. Graham, L. Zheng, D. StJohn, M. Frost, Alloying of pure magnesium with Mg 33. 3 wt-% Zr master alloy, Mater. Sci. Tech. 19(2003)156-162.

DOI: 10.1179/026708303225010849

[7] M. Qian, D. H. StJohn, M. T. Frost, Heterogeneous nuclei size in magnesium–zirconium alloys, Scripta Mater. 50(2004) 1115-1119.

DOI: 10.1016/j.scriptamat.2004.01.026

[8] I. Polmear, Light alloys (London: Arnold Press 1995).

[9] M. Bamberger, Structural refinement of cast magnesium alloys, Mater. Sci. Technol. 17(2001) 15-24.

[10] A. K. Dahle, Y. C. Lee, M. D. Nave, P. L. Schaffer, D. H. StJohn, Development of the as-cast microstructure in magnesium–aluminium alloys, J Light Met. 1(2001) 61-72.

DOI: 10.1016/s1471-5317(00)00007-9

[11] T. Motegi, E. Yano, Y. Tamura, E. Sato, Clarification of grain refining mechanisms of superheat-treated Mg-Al-Zn alloy castings, Mater. Sci. 350(2000) 191-198.

DOI: 10.4028/www.scientific.net/msf.350-351.191

[12] E. Yano, Y. Tamura, T. Motegi, E. Sato, Grain refining mechanism of cast magnesium alloy AZ91 by superheat treatment, J Jpn. Inst. Light Met. 51(2001) 594-598.

DOI: 10.2464/jilm.51.594

[13] E. Yano, Y. Tamura, T. Motegi, E. Sato, Effect of pure carbon powder on grain refining of cast magnesium alloy AZ 91, J Jpn. Inst. Light Met. 51(2001) 599-603.

DOI: 10.2464/jilm.51.599

[14] D. Qiu, M. X. Zhang, J. A. Taylor, P. M. Kelly, A new approach to designing a grain refiner for Mg casting alloys and its use in Mg–Y-based alloys, Acta Mater. 57(2009) 3052-3059.

DOI: 10.1016/j.actamat.2009.03.011

[15] E. R. Davidson, S. Chakravorty, A test of the Hirshfeld definition of atomic charges and moments, Theor. Chim. Acta. 83(1992) 319-330.

DOI: 10.1007/bf01113058

[16] M. Segall, C. Pickard, R. Shah, M. Payne, Population analysis in plane wave electronic structure calculations, Mol. Phys. 89(1996) 571-577.

DOI: 10.1080/002689796173912

[17] M. Segall, R. Shah, C. Pickard, M. Payne, Population analysis of plane-wave electronic structure calculations of bulk materials, Phys. Rev. B. 54(1996) 16317.

DOI: 10.1103/physrevb.54.16317