Thermodynamic Analysis of the Phase Equilibria in the Nb-Ni-Zr System

Abstract

A thermodynamic study of phase equilibria in the Nb-Ni-Zr system has been carried out experimentally and using the CALPHAD method. To enable the thermodynamic description of the constituent binary systems, the results from a previous evaluation were adopted for the Nb-Ni, Ni-Zr and Nb-Zr systems. However, some modifications of the thermodynamic parameters of the Ni-Zr system were made based on recent experimental data on the binary and ternary phase equilibria. The phase boundaries involving the liquid phase in the Nb-Ni-Zr ternary system at the constant 60 mol%Ni and 20 mol%Zr were determined experimentally using differential scanning calorimetry (DSC). The thermodynamic parameters of the Nb-Ni-Zr ternary system were evaluated by combining the experimental results from DSC with reported phase boundaries of the isothermal sections at 773 and 1073 K. The calculated results reproduced the DSC results as well as the experimental isothermal sections. Furthermore, the amorphous-forming ability of Nb-Ni-Zr ternary alloys was evaluated by incorporating the thermodynamic properties from the phase diagram calculations into the Davies-Uhlmann kinetic formulations. The calculated critical cooling rates in the observed metallic glass forming compositional range were found to be lower than those in the observed amorphous forming range by one or more orders of magnitude.

Developments in the Ni–Nb–Zr amorphous alloy membranes

“…Tokunaga et al [68] employed thermodynamic modeling using CALPHAD methodology to determine the glassforming compositional region in the ternary Ni-Nb-Zr phase diagram; results were somewhat comparable with experimental results, but an order of magnitude lower than experimentally observed range. Density functional theory (DFT) calculations were reported as a reliable method for predictions of amorphous membranes for hydrogen permeation and purification by Hao and Sholl [69].…”

Crystalline phases found in rapidly quenched Ni–Nb–Zr alloys

“…The XRD and SAD patterns confirmed the identities of these phases as shown in Figures 2 and 3, respectively. Part of the Ni-Nb phase diagram calculated by Tokunaga et al (2007) is shown in Figure 6 and the dashed vertical line denotes a binary alloy composition close to the investigated ternary alloy composition. As expected from this diagram, solidification occurs by the formation of primary Ni 3 Nb dendrites followed by the eutectic reaction producing Ni 3 Nb and Nb 7 Ni 6 .…”

“…6. Part of the binary Ni-Nb phase diagram as calculated by Tokunaga et al (2007), with an alloy composition that is close to that of Alloy 1.…”

“…Only a limited amount of research has been developed about the crystalline phases in the Ni-Nb-Zr system. Tokunaga et al reported the most recent versions of the binary Ni-Nb, Nb-Zr and Ni-Zr phase diagrams, as well the isothermal sections of the Nb-Ni-Zr ternary system at 500°C and 800°C over the entire composition range (Tokunaga et al, 2007).…”

Thermodynamic investigation of liquid properties of the Ni–Sn–Ti ternary system using CALPHAD method and geometric models

“…The binary systems were thermodynamically investigated and used in the calculations. Three systems: Ni-Sn Gandova (2016), Liu et al (2004), Ni-Ti Gandova (2016), Tokunaga et al (2004) and Sn-Ti Yin et al (2007) exibit large number of intermediate phases.…”