Experimental Verification of Magnetically Induced Phase Separation in αCo Phase and Thermodynamic Calculations of Phase Equilibria of Co-W System

Abstract

Phase equilibria of solid phases in the Co-W system have been investigated by using two-phase alloys and diffusion couple technique. In addition, systematic studies of magnetic and martensitic transitions have been conducted by using Differential Scanning Calorimeter (DSC), Vibrating Sample Magnetometer (VSM) and dilatometric measurement. Two-phase separation into ferromagnetic αCo and paramagnetic αCo was confirmed in the Co-rich side. The Curie temperature and saturation magnetization decrease with increasing W content and those disappear at around 25 at%W. Furthermore, thermodynamic assessment by using CALPHAD approach has been performed. A set of thermodynamic values for describing the Gibbs energy of Co-W system yields a good agreement with experimental phase diagram. The calculation of metastable magnetically induced phase separation along the Curie temperature is also presented.