A thermal fluid dynamics framework applied to multi-component substrates experiencing fusion and vaporisation state transitions

Modelling the dynamics of multi-component alloy systems under extreme conditions and predicting the resulting compositions is a complex task. Here, the authors develop a theoretical framework to predict vaporisation and condensation in multi-component flows during electron beam welding and demonstrate how these processes lead to chemical heterogenisation. The fluid dynamics of multi-component alloy systems subjected to high energy density sources of heat largely determines the local composition, microstructure, and material properties. In this work a multi-component thermal fluid dynamics framework is presented for the prediction of alloy system development due to melting, vaporisation, condensation and solidification phenomena. A volume dilation term is introduced into the continuity equation to account for the density jump between liquid and vapour species, conserving mass through vaporisation and condensation state changes. Mass diffusion, surface tension, the temperature dependence of surface tension, buoyancy terms and latent heat effects are incorporated. The framework is applied to describe binary vapour collapse into a heterogeneous binary liquid, and a high energy density power beam joining application; where a rigorous mathematical description of preferential element evaporation is presented.