Ti-17 volatilization under vacuum: Investigation of the activity coefficients at 1900 °C

Abstract Vacuum processing techniques are a valuable industrial tool for the processing of reactive metals and alloys. However, drawbacks caused by the selective volatilization of alloying elements lead to an hard prediction of final alloy composition. By understanding the behaviour of the alloying elements and the interactions between them, improved compositional accuracy can be achieved. The evaluation of the activity coefficients is a key property that relates partial vapor pressure with the Langmuir law to accurately predict the mass flux of the individual elements in an alloy. This study takes a look at the grade Ti-17 which exhibits a relative large number of alloying elements. By using an electron beam furnace and a vapor deposition apparatus the necessary measurements were made to evaluate activity coefficients for each of the volatizing elements in the alloys including Aluminum, Chromium, Tin. Comparisons were made between experiments and the findings suggest that the primary interactions between the alloying elements with titanium result in small deviations between alloys. The results for the experiments provided reliable and repeatable results.