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Loss of mass due to evaporation during molten metal levitation processing significantly influences the evaluation of density, viscosity and surface tension during thermophysical property measurement. Since there is no direct way to track the evaporation rate during the process, this paper describes a mathematical approach to track mass loss and quantify any changes in alloy composition as a function of time and temperature. The Ni-based super alloy CMSX-4 Plus (SLS) was investigated and a model was developed to predict the dynamic loss of mass with time and track the potential for composition shifts throughout each thermal cycle based on the Langmuir's equation for ideal solution behavior. Results were verified by post-test chemical analysis of key elemental constituents including Al, Cr, Ti, and Co where the error in composition for each element was less than 1% when the activity of aluminum in solution was fixed at zero - effectively eliminating evaporation of aluminum for ground-based electrostatic levitation (ESL) testing in vacuum. This model predicts the mass evaporation for Al and Co within ± 6% errors for CMSX-4 plus samples processed in ESL. Application of this technique to the space tests using the ESA ISS-EML facility shows that by conducting experiments in an inert shielding-gas environment, composition shifts due to differential relative evaporation become negligible and the composition is maintained within the desired limits. By tracking overall mass loss during testing the influence of evaporation on density measurements is discussed. [ABSTRACT FROM AUTHOR]

The solidification path of directionally solidified Ni-based superalloys is an important feature to define the heat treatments necessary after casting. Ni-based superalloy CMSX-10 was solidified at different velocities in a modified Bridgman type furnace allowing rapid quenching of the samples in water. The results of the experiments allowed to clarify the solidification of the interdendritic region, from nucleation of fine γ′ precipitates at the primary γ dendrite surface to the spatial growth and coarsening of the interdendritic colonies' morphology towards the end of solidification. A three-dimensional model is proposed and explains the different morphologies in the interdendritic region according to the observation plane. The study revealed strong evidence of a solidification in the interdendritic region of peritectic nature. Solute rejection into the liquid ahead of the growing phases, diffusion and convection effects lead to the coupled growth of the γ and γ′ phases according to the reactions L → γ and L + γ → γ′ respectively. [ABSTRACT FROM AUTHOR]