A model of the ductile-brittle transition of partially crystallized amorphous Al-Ni-Y alloys

A model of the ductile-brittle transition of partially crystallized amorphous Al-Ni-Y alloys is proposed. The strength of the partially crystalline Al-Ni-Y alloys was found to exhibit a maximum when the size of Al particles is 10 nm. Partially crystallized Al-Ni-Y alloys were also found to be brittle when the size and the volume fraction of the Al particles exceeded the optimum values. On the assumption that the diffusivity of Y is so low that Y atoms rejected from f.c.c.-Al particles are limited near the interface region and the diffusivity of rejected Ni atoms is so high that the perfectly mixed solution is readily attained in the matrix, the reactions in three regions, Al particles, Y accumulated interface layers and amorphous matrix, were derived by balancing the quantify of each element. Al-Ni-Y alloys were assumed to become brittle when the solute content of the interface layers reached the critical value (20%). The predictions based on the Y accumulation model are in good agreement with the published data available. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.