Structures and properties of bulk glass forming NiNbSn alloys and NiNbTaSn alloys

Ternary Ni60Nb40−xSnx (3 ≤ x < 9 at.%) and quaternary Ni60(Nb100−xTax)34Sn6 (x = 20, 40, 60 and 80 at.%) Ni-base alloys were found to form bulk amorphous structures using conventional metallic-mold casting. These bulk amorphous alloys have very high glass transition temperatures (881 K < Tg < 895 K). They also exhibit high Young's modulus (180–200 GPa), shear modulus (54–59 GPa), estimated strength (3–3.8 GPa) and measured compressive yield strength (2–2.8 GPa). The measured strength of the ternary alloys depends strongly on the Sn content and is generally lower than the strength estimated from modulus and hardness. Small-angle neutron scattering studies show that phase separation occurs in these alloys. The phase separation may be responsible for the strong composition dependence of the measured strength and the obvious discrepancy between the measured and the theoretical strengths (i.e. the premature fracture behavior).