Small-angle x-ray-scattering study of phase separation and crystallizationin the bulk amorphous Mg62Cu25Y10Li3 alloy

We report on a small-angle x-ray-scattering (SAXS) and differential scannin g calorimetry study of phase separation and crystallization in rapidly quen ched amorphous Mg62Cu25Y10Li3 alloy samples. Differential scanning calorime try demonstrates the occurrence of crystallization and grain growth upon is othermal annealing of these samples at 135 degrees C. The SAXS studies show the presence of large inhomogeneities even in the rapidly quenched as-prep ared Mg62Cu25Y10Li3 alloy that is attributed to phase separation in the und ercooled liquid during the cooling process. After isothermal annealing at 1 35 degrees C for longer than 30 min the samples exhibit a strong SAXS inten sity that monotonically increases with increasing annealing time. During he at treatment, crystallization and growth of a nanocrystalline bcc-ME,li,pha se occurs in the Y-poor and MgLi-rich domains. The initially rough boundari es of the nanocrystals become sharper with increasing annealing time. Anoma lous small-angle x-ray-scattering investigations near the Cu K edge indicat e that while Cu is distributed homogeneously in the as-prepared sample, a C u composition gradient develops between the matrix and the bcc-Mg7Li3 nanoc rystals in the annealed sample. [S0163-1829(99)01018-8].