Effect of Si, Pd and La additions on glass forming ability and thermal stability of Zr-Ni-based amorphous alloys

In the the present paper, the influence of minor additions of Si, Pd and La with representative atomic sizes on glass forming ability (GFA) and thermal stability of Zr-Ni-based amorphous alloys has been investigated using X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). The results show that minor additions of La. Pd and Si can improve GFA of Zr-Ni-based alloys and La exhibits the optimum effect on enhancing GFA. The efficient cluster packing model can well explain the correlation between atomic sizes of additional elements and GFA of amorphous alloys. In addition, the relationship of the atomic size between the additional element and Zr has a more important effect on GFA than that between the additional element and Ni. The activation energy for crystallization of the Zr-Ni-based amorphous alloys with Si, Pd and La additions is obviously higher than that of the Zr66.7Ni33.3 amorphous alloy, and increases with decreasing distance between neighboring atoms. The thermal stability has a relation with topological short-range ordering of amorphous alloys. The proper addition of small atoms is preferential to enhance thermal stability of amorphous alloys due to stronger short-range ordering. Moreover, the small or intermediate atom addition can produce even better effect on thermal stability than the large atom addition. (C) 2010 Elsevier B.V. All rights reserved.