A Study on the Development of Ni-Based Alloys with Wide Supercooled Liquid Region

Abstract

Ni-based amorphous alloys with wide supercooled liquid region (ΔT_x) have been developed through alloy design based upon the empirical rules for high glass forming alloys. The amorphous Ni₅₉Zr₂₀Ti₂₁ alloy shows glass transition temperature of 794 K, onset temperature of the first exotherm (T_x1) of 808 K and supercooled liquid range (ΔT_x=T_x1−T_g) of 14 K, while the amorphous Ni₅₉Zr₂₀Ti₁₆Si₅ alloy shows T_g of 830 K, T_x1 of 876 K and ΔT_x of 46 K . The amorphous Ni₅₉Zr₂₀Ti₂₁ and Ni₅₉Zr₂₀Ti₁₆Si₅ alloys crystallize through two step reactions. First, primary crystallization of cubic NiTi(Zr) phase occurs from the amorphous matrix and then the NiTi(Zr) and remaining amorphous phases transforms into a mixture of cubic NiTi(Zr) and orthorhombic Ni₁₀(Zr, Ti)₇ phase for the ternary alloy and into a mixture of the cubic NiTi(Zr), orthorhombic Ni₁₀(Zr, Ti)₇ and an unidentified phase containing Si for the quaternary alloy. Partial replacement of Ti by Si improves glass forming ability. A bulk amorphous Ni₅₉Zr₂₀Ti₁₆Si₅ rod with 2 mm in diameter is fabricated by injection casting.