Thermal stability and mechanical strength of bulk glassy Ni-Nb-Ti-Zr alloys

Bulk glassy Ni-based alloys with high fracture strength exceeding 2700 MPa were prepared in Ni60Nb40-x-yTixZry system by copper mold casting. The glassy alloys with distinct glass transition were obtained in the wide composition range from 0 to 35% Ti and 0 to 30%Zr and the largest supercooled liquid region before crystallization was 76K for Ni60Nb15Ti10Zr15. The maximum diameter was 2 mm for Ni60Nb20Ti15Zr5 and the glass transition temperature (T-g), crystallization temperature (T-x) and reduced glass transition temperature (T-g/T-l) of the bulk glassy alloy were 841 K, 898 K and 0.61, respectively. The Young's modulus (E), compressive fracture strength (sigma(c.f)) and compressive fracture elongation (epsilon(c,f)) were 156 GPa, 2770 MPa and 2.4%, respectively, for the bulk alloy. There is a tendency for fracture strength to increase with increasing E, T-g and liquidus temperature (T-l). It is therefore interpreted that the high strength is due to strong bonding nature among the constituent elements.