A study on the development of Ni-based alloys with wide supercooled liquid region

Abstract

Ni-based amorphous alloys with wide supercooled liquid region (ΔTx) 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 (Tx1) of 808 K and supercooled liquid range (ΔTx = Tx1 - Tg) of 14 K, while the amorphous Ni59Zr20Ti16Si5 alloy shows Tg of 830 K, Tx1 of 876 K and ΔTx 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.