Diffusion models for evaporation losses during electron-beam melting of alpha/beta-titanium alloys

An analysis of the evaporation of aluminum during electron-beam melting (EBM) of alpha/beta-titanium alloys was performed. The analysis was based on the solution of the one-dimensional diffusion equation for the solute-concentration gradient in the melt pool subject to the flux boundary condition for the evaporation rate at the melt surface quantified using the Langmuir equation. The effect of process parameters and material coefficients (e.g., the diffusivity and solute activity in the melt) on predicted concentration gradients and melt losses under steady-state melting conditions was established for both the finite-domain and the semi-infinite-domain diffusion problems. The accuracy of the modeling approach was validated by comparison to previous measurements for the EBM of alloys with a nominal Ti-6Al-4V composition.