W0324

In-Situ Synchrotron Study of Phase Separtaion in Bulk Metallic Glass By Simultaneous Diffraction and Small Angle Scattering Measurements. X.-L. Wang^1,2, J. Almer³, Y.D. Wang¹, J.K. Zhao¹, C.T. Liu², A.D. Stoica¹, D.R. Haeffner³, and W.H. Wang⁴, ¹Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA, ²Metals and Ceramics Div., Oak Ridge National Laboratory, Oak Ridge, Oak Ridge, TN 37831, USA, ³Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA, ⁴Inst. of Physics, Chinese Academy of Sciences, Beijing 100080, P. R. China.

Controlled decomposition of bulk metallic glass precursors offers a promising way for synthesis of nanostructured materials in large quantities. By making simultaneous time-resolved measurements of diffraction and small angle X-ray scattering data, we show that the decomposition in Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ bulk metallic glass proceeds in stages, with distinctively different kinetics. Rapid phase separation occurred in the early stage, followed by an abrupt amorphous-to-crystalline phase transformation. The late stage of the decomposition is characterized by slow growth of the nanometer sized crystalline precipitates. These experimental observations support the view that nucleation of the crystalline phase is achieved via phase separation through a mechanism of short-range diffusion of small atoms (e.g., Ni, Cu) whereas the growth is determined by the long-range diffusion.

Research sponsored by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract DE-AC05-00OR22725 with UT-Battelle, LLC.