Control of Al content during ISM process of Nb₃Al 1

The activity coefficients of components in Nb₃Al melt were calculated. On the basis of the activity coefficients, the evaporation behaviors, including the evaporation dynamic and the evaporation loss of Al in the Nb₃Al melt during the induction skull melting (ISM) process were studied systematically. The results show that the evaporation-controlling mode of Al in the alloy melt is a double controlling mode, i.e. the diffusion of evaporation element in melt boundary layer and the evaporation reaction, under the conditions that p = 1.333 Pa and the scope of melt temperature is 2 235-2 635 K. When the melt temperature is 2 385 K(the superheat is 100 K), the evaporation-controlling mode varies from the double controlling mode to a single controlling mode (the evaporation reaction on the surface of melt) if the vacuum chamber pressure is above 133 Pa.