A study of glass-formation, formation of the supercooled liquid and devitrification behavior of Ni-based bulk glass-forming alloys

Abstract

Glass-formation and devitrification of the glassy phase in the Ni–Nb–Zr–Ti and Ni–Nb–Zr–Ti–NM (NM, noble metals) system alloys exhibiting the supercooled liquid on heating were investigated. The crystallized structure and kinetics of devitrification of Ni–Nb–Zr–Ti–Pd glassy alloy are studied in detail. The formation of the glassy single phase has been proven using high-resolution transmission electron microscopy (TEM). The addition of Zr and Pd increases the supercooled liquid region of the Ni 60Nb 25Ti 15 (numbers indicate at.%) alloy from 44 K to about 50 K. The cP2 TiNi phase was found to form during the first exothermic phase transformation in all studied alloys. The addition of Zr to Ni–Nb–Ti alloy prevents formation of oP8 Ni 3Nb phase observed in the Ni 60Nb 25Ti 15 alloy and initiates formation of the primary Ni 10Zr 7 phase while the additions of both NM and Zr effectively refine cP2 TiNi particles size. Definite fractions of rhombohedral R and hR14 Ni 4Ti 3 phases were also observed in NM-bearing alloys. Significantly lower growth rates of the devitrification products in the NM-bearing alloys compared to the Ni–Nb–Ti one may be the reason for the improvement of glass-forming ability (GFA).