固体CaOと平衡するNi-Ca-OとNi-Ta-Ca-O融体の熱力学

抄録

The deoxidation equilibrium of calcium in liquid nickel has been measured by the sampling technique at the temperature ranges from 1873 to 1973 K using calcia crucibles. The effect of tantalum on the activity coefficient of oxygen in liquid nickel have been also investigated in order to understand the effect of the alloying element on the activity coefficient of oxygen for the production of superalloys.
The effect of temperature on the equilibrium constants, K_ca (= a_ca ·a_o/a_cao), for the deoxidation reaction in liquid nickel, i.e:
CaO(s) =Ca+O
was found to be :
logK_ca = - 19430/T + 5.35
while the temperature dependence of the deoxidation product, K'_ca ( = [%Ca] [%O]), and the effect of calcium on the activity coefficient of oxygen in liquid nickel were determined by the expressions :
logK'_ca = logK_ca - (-75900/T +28.7) ( [%Ca] +2.51 [%O])
logf ^ca _O=(-75900/T + 28.7) [%Ca] 0.01 < mass%Ca < 0.13
The results below 0.01mass% calucium obtained at 1973K have been discussed.
Further, the effect of tantalum on the activity coefficients of oxygen and calcium in liquid nickel-tantalum alloys at 1873 K were given by :
logf^Ta _O + logf^Ta _Ca = - 0.12 [%Ta] mass%Ta <4.