Nanostructural transformation and mechanical property variation of Zr-Ti-Al-Cu-Ni bulk amorphous alloys

The evolution of nanocrystalline microstructures from the Zr57Ti5Al10Cu20Ni8 bulk amorphous alloy was studied under various annealing conditions. The transformation of the nanocrystalline microstructures is referred to the low growth rate of the precipitated crystals and the increasing thermal stability of the residual amorphous phase during annealing. The partially crystallized alloys exhibit higher yield stress and fracture stress than the as-cast amorphous alloy and maintain good ductility when the precipitated crystal fraction is less than about 40 vol.%. The strength and the ductility decrease with further increase of the crystalline volume fraction. The good mechanical properties of the partially crystallized alloy are attributed to the microstructure of nanocrystals embedded homogeneously in the residual amorphous matrix which maintains the deformation mechanism typical for the amorphous phase.