Determination of thermodynamic interaction parameters in solid V-Ti-Cr alloys using the mass spectrometer

The Knudsen effusion method was combined with a mass spectrometer sensing technique in order to determine thermodynamic interaction parameters of solid solution bcc alloys of V-Ti-Cr. A regular solution model was used to relate the vaporization data to ion current ratios obtained from the mass spectrometer. The temperature range of the vaporization experiments was 1400° to 1700°C, with alloy compositions ranging from 10 to 66 at. pct of each of the three components in the ternary system. Modified interaction parameters were calculated by assuming only binary interactions (which is a good approximation at low third component concentrations). The results are: Ω _TiV = 1.8 ± 0.2 kcal/g-atom; 0 <N _Cr < 0.2 ({iT} _AV = 1800 K) Ω _TiCr = 1.9 ± 0.4 kcal/g-atom; 0.1 <N _V < 0.4 ({iT} _AV = 1750 K) Ω _VCr = 3.1 ± 0.7 kcal/g-atom; 0.1 <N _Ti < 0.4 ({iT} _AV = 1850 K) A temperature dependent form was an appropriate refinement of the results for the Ti-Cr system from 1500 to 1840 K. That expression is $$Omega {text{ = 28 (1 - }}frac{T}{{1840 K}}{text{ kcal/g - atom}}$$ Overall, experimental results show important, but not complete, agreement with estimates from phase diagrams and theoretically calculated values.