Thermodynamic properties of Ti in V-Ti-Ta alloys: Effect of Ta addition

Abstract The vaporization behaviour of Ti in V-4Ti-xTa (x = 0,1,3,7 wt%) alloys has been investigated in the temperature range 1960–2120 K by Knudsen effusion mass spectrometry (KEMS). The partial pressures and thermodynamic activities of Ti were evaluated directly from the measured ion intensities formed from the equilibrium vapor over the alloy. From the temperature dependence of the activity, the partial molar enthalpy of mixing, partial and excess free energy of mixing has been obtained. The following partial pressures could be obtained over the alloys: V-4Ti logp = −(2.15 ± 0.095) 104/T + (4.38 ± 0.46) 1958–2065 K V-4Ti-1Ta logp = −(2.64 ± 0.043) 104/T + (6.754 ± 0.21) 1961–2070 K V-4Ti-3Ta logp = −(2.41 ± 0.043) 104/T + (5.38 ± 0.21) 1920–2052 K V-4Ti-7Ta logp = −(3.00 ± 0.21) 104/T + (8.02 ± 1.0) 2050–2119 K It was observed that activity of Ti decreases from 0.036 to 0.010 as Ta content increases from 0 to 7 wt% in V-4Ti-xTa alloys.