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 Zr_70−yNb_xCu_30−xAl_y (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.