Nanocrystal composites in Zr-Nb-Cu-Al metallic glasses

Adding Nb to Zr-Cu-Al amorphous alloys induces the primary transformation occurring on heating. Nanocrystalline-amorphous composites were produced by annealing Zr70-yNbxCu30-xAly (X= 5-7.5 and y= 8-12 at.%) metallic glasses. Their structures, after completing the primary transformation by annealing, were found to consist of fine crystals with a scale less than 15 nm dispersed homogeneously in an amorphous matrix. The nanostructured alloys show increased tensile strength and hardness with good bending ductility at a volume fraction of nanoparticles less than 50%,. We suggest that the stronger attractive interaction between Zr-Al is the reason of the presence of the quenched-in embryos in as-solidified samples, and the quenched-in embryos therefore provide nucleation sites for nanocrystal formation. (C) 2000 Elsevier Science B.V. All rights reserved.