STUDY OF U-10 % Zr ALLOY PROPERTIES

Density, phase composition, microstructure and thermal conductivity of the U-10 wt. % Zr alloy manufactured by induction melting with subsequent casting into quartz molds and turning to size have been investigated at JSC “SSC RF - IPPE”. For comparison, the density and thermal conductivity of the U-10 wt. % Zr alloy produced by melting followed by extrusion and turning to size were investigated. To determine the density, a hydrostatic weighing method was used. The average density values of the cast and extruded alloy were respectively 98.8 and 97.5 % of the theoretical density, which was calculated according to the rule of mixtures. The results of studying the microstructure using a scanning electron microscope are presented. It is shown that the cast alloy U-10 % Zr is a metal matrix in which zirconium-enriched particles of arbitrary shape are distributed. In a metal matrix, the bulk of the volume is occupied by the α-U, and there are also precipitates of the δ-phase in the form of thin plates. A lower value of the microhardness of the alloy is noted in comparison with the data published in the known literature. The results of measuring the thermal conductivity at temperatures from 100 to 750 °C for the U-10 wt. % Zr alloy obtained by casting and extrusion are presented. The stationary axial heat flux method (or method of plate) was used to measure the thermal conductivity. Alloy samples made in different ways have almost the same thermal conductivity at 200 °C. With an increase in temperature, the discrepancy in thermal conductivity between the samples of the cast and extruded alloy gradually increases, and the thermal conductivity of the extruded alloy turns out to be lower, which is especially noticeable in the temperature range of 600-750 °C. The data obtained are compared with the results of published works. The measured values of the thermal conductivity of the cast alloy U-10 wt. % Zr up to a temperature of 750 °C do not disagree with the literature data. It was found that at a higher temperature, the alloy softens, which, in turn, leads to deformation of the test specimen and an increase in the measurement error when using the axial heat flux method.