Ni-based bulk metallic glass formation in the Ni-Nb-Sn and Ni-Nb-Sn-X (X = B,Fe,Cu) alloy systems

Refractory Ni-based bulk metallic glasses are formed in the three-component Ni-Nb-Sn system near a ternary eutectic composition located within the three-phase field bounded by the three intermetallics Ni3Nb, Ni6Nb7 (mu-phase), and Ni2NbSn (BiF3-type). Bulk amorphous alloys of composition Ni60Nb40-xSnx with 3<9 were prepared by injection-casting the molten alloys into copper models. X-ray diffraction and differential scanning calorimetry studies show the cast strips to be fully amorphous up to thicknesses from 0.5 to 3 mm as x is varied. Maximum glass-forming ability (GFA) observed when x is between 6 and 7. These refractory bulk amorphous alloys exhibit high glass transition temperatures 881<895 K, a large, stable, undercooled liquid region with DeltaT=T-x-T-g, at similar to40-60 K, very high Vickers hardness (VHsimilar to1000-1280 Kg/mm(2)), and estimated yield strengths in the range of 3 to 3.8 GPa. The effects of small quaternary additions of B and Fe on the GFA of the ternary alloys are also reported. (C) 2003 American Institute of Physics.