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

Abstract

New Ni-based bulk metallic glasses were synthesized in Ni x Cu a − x Ti y Zr b − y Al 10 ( a∼ b∼45 at.%) system, based on a ternary alloy, Ni 45Ti 20Zr 35. The additions of Al and Cu greatly increase the glass-forming ability (GFA). The best GFA is located around Ni 40Cu 5Ti 16.5Zr 28.5Al 10, 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∼760 to 780 K, and relatively wide undercooled-liquid regions Δ T (defined by the difference between T g and the first crystallization temperature T x1 upon heating) ∼40–50 K. Mechanical tests on these alloys show quite high Vicker's Hardness ∼ 780 to 862 kg/mm 2, Young's modulus ∼ 111 to 134 GPa, shear modulus ∼ 40 to 50 GPa and high fracture strength ∼ 2.3 to 2.4 GPa. The effect of small Si-addition and a discrepancy between GFA and Δ T are also reported. The exceptional GFA and the all-metallic compositions give these new alloys excellent promise for both scientific and engineering applications.