Abstract:Based on Kohler’s ternary solution model and Miedema model for calculating the heats of formation—ΔHijof binary systems, the activity coefficients in Ti-15-3 melt have been calculated. Taking advantage of the activity coefficients and the corrected Langmuir Equation, the evaporation losses of components in Ti-15-3 melt during ISM process have been studied. The calculated results prove Ilschner’s statement of existing a critical vacuum degree (about 1.33 Pa) during melting process under the vacuum condition. When the vacuum degree in the vacuum chamber surpasses this value, the evaporation of components takes on a state of free evaporation. Finally, the calculated results are compared with the experimental data, which testifies the reliability of the models for calculating activity coefficients and evaporation losses.

Key words: Ti-15-3 alloy　evaporation loss　ISM process