Letter abstract
Nature Materials 6, 192 - 197 (2007)
doi:10.1038/nmat1839
Subject Categories: Metals and alloys | Mechanical properties
Polyamorphism in a metallic glass
H. W. Sheng1, H. Z. Liu2,3, Y. Q. Cheng1, J. Wen4, P. L. Lee5, W. K. Luo1, S. D. Shastri5 and E. Ma1
A metal, or an alloy, can often exist in more than one crystal structure. The face-centred-cubic and body-centred-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions1, 2, 3, 4, 5, 6, 7 in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral4, 5) coordination environments. Here, we report an in situX-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce55Al45 metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modelling of the effects of f-electron delocalization8, 9, 10. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties11 due to different bonding and structural characteristics.
- Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
- HPCAT, Geophysical Laboratory, Carnegie Institution of Washington, Building 434E, 9700 South Cass Avenue, Argonne, Illinois 60439, USA
- Center for the Condensed Matter Science and Technology, Harbin Institute of Technology, Harbin 150080, China
- Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, China
- XOR, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
Correspondence to: H. W. Sheng1 e-mail: hwsheng@jhu.edu
Correspondence to: E. Ma1 e-mail: ema@jhu.edu
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