Segregation-controlled nanocrystallization in an Al-Ni-La metallic glass

Abstract

The early stages of devitrification of Al89 Ni6 La5 metallic glass were investigated using three-dimensional atom probe. Even in the as-quenched amorphous state, nanometer-sized fluctuations of Ni and Al were observed. The Al-rich fluctuations act as nucleation sites for the crystallization at 443 K in which α-Al clusters with a number density up to 5× 1023 m-3 nucleate and grow to nonspherical, 12 nm large crystals. α-Al particles are almost pure in Al and are surrounded by a La-rich shell. It is concluded that La segregation controls the growth and limits the size of the α-Al nanocrystals. © 2008 American Institute of Physics.