Phase diagrams of the ternary systems U-Th-Mn, Fe and Ni in a part rich in uranium and thorium

The report contains the results of experimental studies phase diagrams of the ternary systems U-Th-Mn, -Fe and -Ni. The authors carried out thermal and microstructural analyses of the alloys and measured their hardness and microhardness. Projections of the liquidus surfaces and phase diagrams are constructed and reaction diagrams drawn up. A characteristic feature of the systems studied is the existence of zones of stratification in the liquid phase which spread to the ternary systems from the binary U-Th system and of four-phase eutectic equilibria in the vicinity of binary, uranium-rich eutectics of uranium with manganese, iron and nickel. In the U-Umn2-Th system, four-phase eutectic equilibrium exists at 730degC; there are also two four-phase peritectic equilibria, at 775degC and 740degC, and a peritectoid and a eutectoid equilibrium. The zone of stratification in the liquid phase spreads to the ternary system at manganese concentrations of up to approximately 18 at.% Mn. In the U-UFe2-Th system, four-phase eutectic equilibrium is established at 720degC; there are two peritectic equilibria, at 805degC and 800degC; in the solid phase two eutectoid equilibria are observed. There is no zone of stratification in the liquid phase, even at 2 at.% Fe. In the system U-U7Ni9 -ThNi-Th, four-phase eutectic equilibrium exists at 735degC. In this system there are also two monotectoid four-phase equilibria, at 1650degC and 1050degC, and five peritectic equilibria, at 1040degC, 1020degC, 800degC, 785degC and 780degC; in the solid phase, eutectoid conversions are observed. The zone of stratification in the liquid phase occupies a significant part of the system concentration range studied by the authors, reaching 36 at.%Ni and 64 at.%Th