APPLIED PHYSICS GROUP
Prof. Xun-Li WANG
Chair Professor, Department of Physics
Executive Director, Hong Kong Institute for Advanced Study
City University of Hong Kong
Structure and Phase Transformation in Amorphous Alloys
The nature of the glassy state is one of the top 100 scientific grand challenges identified by Science magazine. Amorphous materials have no long-range order, but there are ordered structures at short-range, medium-range, and even longer length scales. We are interested in the atomic packing in amorphous alloys, and how the packing change under heating or deformation. The outcome of these studies will help elucidate the following issues
- Structure and stability of amorphous alloys
- Structure – property relationship
- Liquid-to-liquid phase transition
- The nature of glass transition
In this example, in situ time-resolved synchrotron diffraction measurements identified a hidden amorphous phase and the associated phase transition in a Pd-Ni-P amorphous alloy. The plot shows evolution of pair-distribution function of Pd-Ni-P amorphous alloy as a function of temperature during heating. The solid blue curve is a differential calorimetry scan, which is supposed with the structural evolution. The excellent correlation demonstrates the phase transition. At higher temperatures, the structure reverts to its original structure (reentrant glass state).
(Lan et al., Nature Communications. 2017)
Key publications from our group:
 S. Lan, Y. Ren, X. Y. Wei, B. Wang, E. P. Gilbert, T. Shibayama, S. Watanabe, M. Ohnuma, and X.-L. Wang*, “Hidden Amorphous Phase and Reentrant Supercooled Liquid in Pd-Ni-P Metallic Glasses,” Nature Communications 8, 14679 (2017).
[CrossRef] [Google Scholar] [Featured in Nature Communications collection series, Metallurgy]
 D. Ma, A. D. Stoica, X.-L. Wang*, Z. P. Lu, B. Clausen, D. W. Brown, “Moduli inheritance and the weakest link in metallic glasses,” Physical Review Letters, 108, 085501 (2012).
[CrossRef] [Google Scholar] [Covered by News and Views, Nature Materials]
 D. Ma, A. D. Stoica, and X.-L. Wang*, “Power-law scaling and fractal nature of the medium range order in metallic glasses,” Nature Materials, 8, 30-34 (2009).
 L. Yang, M. K. Miller, X.-L. Wang*, C. T. Liu, A. D. Stoica, D. Ma, J. Almer, and D. Shi, “Nano-scale solute partitioning in devitrified bulk metallic glass,” Advanced Materials, 21, 305-308 (2009).
[CrossRef] [Google Scholar] (Featured on the cover)
 X.-L. Wang*, J. Almer, Y. D. Wang, J. K. Zhao, C. T. Liu, A. D. Stoica, D R. Haeffner, and W. H. Wang, “In-situ Synchrotron Study of Phase Transformation Behaviors in Bulk Metallic Glass Using Simultaneous X-ray Diffraction and Small Angle Scattering,” Physical Review Letters, 91, 265501 (2003).