Formation, Thermal Stability and Mechanical Properties of Zr-Nb-Cu-Ni-Al Bulk Metallic Glasses

Bulk Zr62-xNbxCu15.4Ni12.6Al10 (x=0–10 at%) glassy alloys were prepared via copper mould casting. XRD, DSC, SEM and compression test show appropriate niobium addition can enhance the glass forming ability (GFA) and thermal stability of these alloys. The bulk amorphous alloy with x=2.5 displays the largest temperature interval of supercooled liquid region ((delta) Tx) up to 105 K and the largest (gamma) value 0.428. However, the largest critical diameter is not achieved at x=2.5 but at x=5 instead, indicating a larger (delta) Tx and (gamma) value does not necessarily mean a higher glass-forming ability. At x=10, no glass transition but crystallization takes place, suggesting too much Nb may promote crystallization. The compression test shows increasing Nb content increases the strength and reduces the plasticity of the Zr62-xNbxCu15.4Ni12.6Al10 glassy alloy, which is apparently attributed to the decrease in the number of microstructural heterogeneities in the metallic glasses, resulting in much less severe multiplication and interaction of shear bands.