Improving the glass-forming ability and the plasticity of Zr-Cu-Al bulk metallic glass by addition of Nb

(Zr47Cu44Al9)(100-x)Nb-x (x = 0, 1, 2, 3, and 5 at.%) bulk metallic glasses (BMGs) were prepared by copper mould casting. The influence of Nb addition on glass-forming ability (GFA), thermal stability and mechanical properties of ZrCuAl alloys was studied. The GFA of Zr47Cu44Al9 BMGs is enhanced obviously after the addition of Nb. The critical size of completely amorphous sample increases from 4 mm for Zr47Cu44Al9 to 10 mm for (Zr47Cu44Al9)(98)Nb-2 alloy. The average activation energy of crystallization is 505 kJ/mol for (Zr47Cu44Al9)(98)Nb-2 BMG, which is larger than that of Zr47Cu44Al9 BMG with 443 kJ/mol. The fracture strength and plasticity are sensitive to the Nb content. (Zr47Cu44Al9)(98)Nb-2 BMG exhibits high fracture strength of 2397 MPa and prominent plastic strain of 13.2%, and multiple shear bands with high density were observed. Furthermore, the possible mechanisms involved in obtaining high GFA and large plasticity were explored.