Nanocrystalline composites with high strength obtained in Zr-Ti-Ni-Cu-Al bulk amorphous alloys

Nanocrystalline composites with the grain size less than 10 nm were produced by annealing of Cu-mold cast Zr70-x-yTixNi10Cu20Aly (X=5-7.5 and Y=10-15 at %) bulk amorphous alloys. The nanostructured alloys show increased tensile strength at the volume fraction of nanoparticles less than 30%. The microstructure of the amorphous alloys was found to contain medium range order (MRO) domains, which uniformly distributed in the amorphous matrix. We suggest that MRO domains provide nucleation sites for precipitation of the primary crystals and lead to the formation of nanocrystalline composites. (C) 1999 American Institute of Physics. [S0003-6951(99)03429-4].