DEOXIDATION EQUILIBRIUM OF SILICON IN LIQUID NICKEL COPPER AND NICKEL COBALT ALLOYS

The deoxidation of liquid nickel-copper and nickel-cobalt binary alloys with silicon has been measured at temperatures ranging from 1 450 to 1 650-degrees-C by the use of quartz crucibles. On the nickel basis in nickel-copper binary, the deoxidation product, log K'Si(Ni-Cu), which increased with the addition of copper up to 40 mass% containing 0.5 mass% silicon, was expressed to be: log K'Si(Ni-Cu)=log K(Si(Ni)+0.0342[%Cu]-0.0004[%Cu]2 The effect of temperature on the equilibrium constants of the deoxidation reaction in copper, obtained by the extrapolation, was estimated as follows: log K(Si(Cu)=-15 680/T + 2.16 while log K'Si(Ni-Cu) on the copper basis was given by the expression: log K'Si(Ni-Cu)=log K(Si(Cu)+0.012[%Ni]-0.0001[%Ni]2 up to 40 mass% of nickel. On the nickel basis in nickel-cobalt binary containing 0.55 mass% silicon, log K'Si(Ni-Co) up to 20 mass% of cobalt was represented to be as follows: log K'Si(Ni-Co)=log K(Si(Ni)+0.005[%Co] The temperature dependence of the equilibrium constants at temperatures between 1 550 and 1 650-degrees-C for the deoxidation of pure cobalt was expressed to be: log K'Si(Co)=-15 270/T + 1.81 whereas logK'Si(Ni-Co) on the cobalt basis was found to be: log K'Si(Ni-Co)=log K'Si(Co)-0.001[%Ni] up to 60 mass% of nickel. Using these values of the deoxidation product, the interaction parameters for the effect of these elements on the activity coefficient of oxygen in metals have been established.