Formation and properties of new Ni-based amorphous alloys with critical casting thickness up to 5 mm

New Ni-based bulk metallic glasses were synthesized in NixCua-xTiyZrb-yAl10() (a similar to b similar to 45 at. %) system, based on a tertiary alloy, Ni45Ti20Zr35. The additions of Al and Cu greatly increase the glass-forming ability (GFA). The best GFA is located around Ni40Cu5Ti16.5Zr28.5Al10, from which fully amorphous samples of up to 5 mm thickness were successfully fabricated by an injection mold casting method. These alloys exhibit high glass-transition temperatures T-g similar to 760 to 780 K, and relatively wide undercooled-liquid regions DeltaT (defined by the difference between T-g and the first crystallization temperature T-x1 upon heating) similar to40-50 K. Mechanical tests on these alloys show quite high Vicker's Hardness similar to780 to 862 kg/mm(2), Young's modulus similar to111 to 134 GPa, shear modulus similar to40 to 50 GPa and high fracture strength similar to2.3 to 2.4 GPa. The effect of small Si-addition and a discrepancy between GFA and AT are also reported. The exceptional GFA and the all-metallic compositions give these new alloys excellent promise for both scientific and engineering applications. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.