Experimental investigation of the Ni-V-W ternary phase diagrams

Abstract

Phase equilibria in the Ni-V-W ternary system have been experimentally investigated. The phases and their compositions of Ni-V-W alloys annealed at 900 and 1100 °C were studied via X-ray diffraction (XRD) and electron probe micro-analysis (EPMA) measurements. The isothermal section measured at 1100 °C showed a three-phase region of fcc + bcc + (σ). Two three-phase regions [fcc + bcc + (σ) and WNi4 + WNi + bcc] were detected in the samples annealed at 900 °C. No ternary compounds were detected in the present work. The solubility of V in the Ni-W binary compounds, i.e. WNi4, WNi, W2Ni, at 900 °C was found to be extremely small (maximum 1.12 at. % V). The solubilities of W in (σ) at 900 and 1100 °C were found to be 2.14 at. % and 3.17 at. %, respectively. The complete isothermal sections at 900 and 1100 °C of the Ni-V-W system were then constructed, which are needed for a thermodynamic optimization of the ternary system.