Abstract
Crystallization behavior and microstructural development during annealing of Al 90 Ni 6 Nd 4 and Al 85 Ni 5 Y 10 glasses were investigated in detail by quantitative TEM. Isothermal annealing for various periods at temperatures between 140°C and 250°C lead to partially nanocrystalline microstructures consisting of a fine dispersion of α-Al nanocrystals embedded in an amorphous matrix. The Al 85 Ni 5 Y 10 glass exhibits a higher thermal stability than Al 90 Ni 6 Nd 4 glass. Nucleation was studied by crystallization statistics of partially crystallized glasses by fitting measured crystal size distributions. Crystallization statistics revealed that the α-Al phase forms by transient heterogeneous nucleation with nucleation rates in the order of 10 20 - 10 21 m -3 s -1 . The nanocrystal growth proceeds rapidly at the beginning, but was found to slow down probably due to the formation of a RE-rich diffusion barrier between the α-Al crystals and the matrix; Nd seems to be even more effective in slowing down the growth than Y.
Published Version
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