Phase behavior and thermodynamics of U-Mo-C system

The U-Mo-C system has been studied to supplement the hitherto available phase-diagram data and to deduce therefrom the thermodynamic property of UMoCsub(1.7) and UMoC2. It is shown that a peritectic four-phase reaction takes place: UC+Mo reversible UMoCsub(1.7)+liquid, at 1,8300+-300C. The phase relations between orthorhombic UMoC2 and monoclinic UMoCsub(1.7) may be defined by UMoCsub(1.7) reversible UMoC2+liquid, which will occur at some temperature between 2,2000 and 2,3500C, the reported melting point of UMoC2. Liquidus projection for the U-Mo-C system is presented on the basis of these results and from data found in literature. The free energy equations for the formation of UMoCsub(1.7) and UMoC2 are respectively estimated to be ΔGsub(f)0(UMoCsub(1.7))=-40,350-0.69T cal/mol and ΔGsub(f)0(UMoC2)=-46,360-0.69T cal/mol, both in the temperature range 298--2,100 K. (auth.)