| New Ni-based bulk metallic glasses were synthesized in NiTiZrNbSi system. Alloys were developed based on the quaternary alloy (A) Ni48,5-Nb21,5-Ti16,5-Zr13,5 (in at.%) applying a small addition of Si. At first, the alloy Ni45-Nb21-Ti16-Zr13-Si5 (alloy B in at.%) was cast and then a new alloy based on the eutectic composition Ni50,34-Nb14,38-Ti17,32-Zr15,15-Si2,81 (alloy C in at.%) has been developed. Both alloys were also prepared by mechanical alloying and melt spinning and in both cases fully amorphous structure was observed. DSC analysis of the ribbon of the alloy B shows crystallization temperature of 512 œC. In the alloy C HRTEM studies indicated presence of a few nanocrystals of size of 1-2 nm in the ribbons and 5-7 nm in the powders. DSC analysis shows crystallization temperature of 555 œC in the ribbon and 587 œC in the powder. The Vickers microhardness measurements gave similar results for both amorphous B and C alloys close to 12G Pa. Ultra high pressure compacting performed under pressure of 4-7 GPa and temperatures several degrees below crystallization temperatures allowed to obtain compacts of dominating amorphous structure as confirmed using TEM studies and DSC measurements. |
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