Evaluation of the Control Mode of Al Element Evaporation during ISM Process of Ti-Al Intermetallics

On the basis of an in-depth analysis of the evaporation process of alloying elements during induction skull melting (ISM) a model for the control mode of element evaporation has been established. The calculated results of Al element evaporation in Ti-48Al-2Cr-2Nb(at%) and Ti-24Al-11Nb(at%) alloys show that when melt temperature increases and/or pressure decreases, the control mode of Al element evaporation changes from an evaporating reaction control mode at low melt temperature and/or under high outer pressure to a double control mode - evaporating reaction and liquid phase diffusion at high melt temperature and/or under low pressure. When the outer pressure is 133. 3 Pa, the transformation temperatures of the control mode of Al element evaporation are approximately 1 950 K and 2 000 K respectively for the Ti-48Al-2Cr-2Nb(at%) and Ti-24Al-11Nb(at%) alloys. While the transformation pressures of the same alloys are approximately 133. 3 Pa and 66 Pa respectively when the melt temperature is 2 073 K. The reason is that the saturated vapor pressures of Al element in various alloys are different.