Merging of Solidus and Liquidus Curves in Copper–Nickel Nanophase Diagram due to Segregation

Abstract

Phase diagram was predicted for Cu–Ni nanoalloy system using regular solution considering various models with and without segregation. Phase diagrams for nanoparticles are affected by the melting point of nanoparticles, and various models are available to predict the melting point for nanoparticles. Hence, choosing the right model helps in accurate nanophase diagram predictions. Three models are considered to predict the melting point of nanoparticles and phase diagrams. Thermodynamic model, enthalpy and entropy model and crystal structure models were compared for their melting points and phase diagram predictions. These three models were then compared with experimental results carried out by Sopousek et al. for a 26 nm particle size. It was found that for a 11.1 Wt% Ni nanoalloy, thermodynamic model accurately predicts the phase diagram with an error of 0.09% compared to enthalpy and entropy model. Thermodynamic model is also known as the surface-phonon instability model which considers various factors like surface phonons, atoms and intrinsic defects in the nanoparticle and hence accurately predicts the melting point and the phase diagram. Further segregation effects were also considered, and for the first time, a comparison between three models is reported which shows significant merging of solidus and liquidus curves in thermodynamic model and enthalpy and entropy model using William–Nason’s model.