^aDCME, Pakistan Institute of Engineering and Applied Sciences, P.O. Nilore, Islamabad, Pakistan

^bPhysics Division, Pakistan Institute of Nuclear Science & Technology, P.O. Nilore, Islamabad, Pakistan

Abstract

Normally, monolithic bulk metallic glasses exhibit poor ductility (<1%) at room temperature through inhomogeneous plastic deformation. Only a few compositions are found so far showing some ductility but their deformation mechanism is still poorly understood. In this letter, a Zr-based bulk metallic glass is presented showing the ductility of 12%. It was observed that loops of material flow are created on shear plane in the initial stages of deformation while river pattern emerges out of these loops in the later stages of deformation. It was also investigated that the intersectioning of shear bands leads to the ductile behavior as well as irregular serrated behavior in stress-strain curve for the alloy.

Keywords: Amorphous materials; Casting; X-ray diffraction; Scanning electron microscopy; Thermal analysis

^aLeibniz-Institute IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden, Germany

^bInstitute for Solid State Research, Forschungszentrum Jülich, P.O. Box 1913, 52425 Jülich, Germany

^cHASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

^dOak Ridge National Laboratory, Oak Ridge, TN 37831-6136, USA

Abstract

Phase-separated Ni–Nb–Y metallic glasses were prepared by rapid quenching from the melt. The early stages of decomposition were characterized in Ni–Nb–Y alloys with Ni contents of more than 60 at.%. Strongly correlated chemical fluctuations with a nanometer length scale were found to exist in the as-quenched state. The observed fluctuation lengths range from 5 to 12 nm, depending on the actual composition of the glass. The “frozen-in” early stages of decomposition occur in the deeply undercooled melt due to the reduction in the critical temperature of liquid–liquid phase separation with Ni content. Annealing of the phase-separated Ni₇₀Nb₁₅Y₁₅ glass below the crystallization temperature leads to an increase in the amplitude of the fluctuations. However, the wavelength was unchanged, which provides evidence for the spinodal character of the decomposition.

Keywords: Phase separation; Metallic glass; Spinodal decomposition; Small angle scattering; Small angle X-ray scattering