The effect of Nb and Pd combination on the glass forming ability (GFA) and mechanical properties of Zr(53)Cu(30)Nb(x)Pd(9-x)Al(8) (x = 3.5-6.0) bulk metallic glasses (BMGs) were systematically investigated by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and compression test. TEM observation revealed that a nanocrystalline phase embeds in the amorphous matrix of the as-cast Zr(53)Cu(30)Nb(4.5)Pd(4.5)Al(8) alloy. A tiny nano-crystalline phase (with size about 5-20 nm) embedded uniformly in the amorphous matrix of the Zr(53)Cu(30)Nb(4.5)Pd(4.5)Al(8) alloy was observed and identified to be the tetragonal structured NbPd(3) phase based on the analyses of nano beam electron diffraction. According to the results of thermal analyses, the composition of Zr(53)Cu(30)Nb(5)Pd(4)Al(8) and Zr(53)Cu(30)Nb(4.5)Pd(4.5)Al(8) present the optimum GFA as well as thermal stability in the Zr(53)Cu(30)Nb(x)Pd(9-x)Al(8) (x = 3.5-6.0) alloy system. In addition, the result of compression test shows that the yield strength significantly increases from 1700MPa (Zr(53)Cu(30)Nb(5)Pd(4)Al(8)) to 1900MPa (Zr(53)Cu(30)Nb(4.5)Pd(4.5)Al(8)). A remarkable compression plastic strain (11.2%) occurs at Zr(53)Cu(30)Nb(4.5)Pd(4.5)Al(8) BMG rod with 2mm in diameter. This significant increase in plasticity is presumably due to the restriction on shear banding by the nano-size second phase. (C) 2011 Elsevier B.V. All rights reserved.
