Evaporation mechanism of aluminum during electron beam cold hearth melting of Ti64 alloy

摘要

Using the Langmuir equation and penetration theory, the evaporation process of Al during the electron beam cold hearth melting of Ti64 alloy under steady state conditions was calculated and the evaporation mechanism was analyzed. The calculation results show that it is necessary to consider both the evaporation step at the liquid/gas surface and the diffusion step in the molten pool during calculation. Comparison of the mass transfer coefficient of the evaporation step and the diffusion step shows that the Al evaporation process is a double controlled process. The Al concentration at the interface decreases from 260 kg m{sup}(-3) to 140 kg m{sup}(-3), and the evaporation rate increases rapidly from 0.001 kg m{sup}(-2) s{sup}(-1) to 0.012 kg m{sup}(-2) s{supo}(-1) when the temperature increases from 1950 K to 2300 K. To control the evaporation loss of Al, surface temperature should be controlled during the electron beam melting of Ti64 alloy.