Notes on the glass-forming ability of bulk metallic glasses

FEB 01, 2014

Jianbo Liu

The article “Bulk metallic glasses” by Jan Schroers in the February 2013 issue of Physics Today (page 32 ) was very enjoyable. The author’s remarks on the recent progress of bulk metallic glasses are much appreciated. However, the author made no mention of original work from Baixin Liu’s group at Tsinghua University in China. I offer this short note as a supplement to Schroers’s article.

Schroers concludes that one can describe a material’s glass-forming ability (GFA) as being either inversely proportional to its critical cooling rate or proportional to its critical casting thickness. Liu and coauthors argued that, more broadly, the GFA of a metal alloy system is quantitatively related to its glass-forming range. ¹ ^, ² The GFR not only shows whether metallic glasses could be obtained in a system, it also indicates the alloy composition range within which metallic glasses could be formed by some specific glass-producing techniques. The wider the GFR, the greater the GFA of a metal system.

Indeed, Jia Hao Li and coworkers from Liu’s group have shown through computations and simulations based on the interatomic potentials of some 10 representative binary metal systems that each system has two critical solid solubilities that define the GFR: For the composition range bounded by the two values, metallic glass formation is energetically favored. The predicted GFRs from the interatomic potentials are well supported by the experimental observations. ² A similar approach applied to some ternary metal systems that form bulk metallic glasses showed not only that the favored composition region (GFR) could be located, but also that an optimal composition, defined as the one having the maximum driving force for crystal-to-amorphous transition, could be pinpointed. ³ I think the predicted optimized composition could be correlated to the maximum size of the metallic glass obtained by copper-mold casting with a specific cooling rate. If so, the physical and technical definitions of GFA could then be bridged.

References

1. Q. Zhang, W. S. Lai, B. X. Liu, Phys. Rev. B 59, 13521 (1999). https://doi.org/10.1103/PhysRevB.59.13521
2. J. H. Li, Y. Dai, Y. Y. Cui, B. X. Liu, Mater. Sci. Eng. R. 72, 1 (2011). https://doi.org/10.1016/j.mser.2010.09.002
3. See, for example, Y. Y. Cui, J. H. Li, Y. Dai, B. X. Liu, J. Phys. Chem. B 115, 4703 (2011). https://doi.org/10.1021/jp200082e

More about the Authors

Jianbo Liu. (jbliu@tsinghua.edu.cn) Tsinghua University, Beijing.