The effect of Al addition on the thermal properties and crystallization behavior of Ni60Nb40 metallic glass

The effect of Al addition to Ni60Nb40 on the thermal property and crystallization behavior of amorphous phase was investigated by using thermal analyses, X-ray diffractometry (XRD) and transmission electron microscopy. As melt-spun amorphous (Ni60Nb40)100−xAlx (x=0, 3, 5, 10 at.%) alloys crystallizes through two exothermic reactions, corresponding to precipitation of nanoscaled crystalline phase followed by formation of the rhombohedral Ni6Nb7 phase and orthorhombic Ni3Nb phase. With increasing the Al content, the first weak exothermic peak shifted to lower temperature region and the second exothermic peak shifted to higher temperature region. The addition of Al promotes the formation of Ni3Al phase in the first exothermic reaction. The amorphous (Ni60Nb40)100−xAlx alloys show low value of heat of crystallization, which may be related with structural similarity between amorphous structure and final crystallization products. Fully amorphous rod with diameter of 1 mm could be fabricated by injection casting (Ni60Nb40)100−xAlx (x=0, 3, 5 at.%) alloys. Further addition of Al deteriorates the glass forming ability.