The Development of Porosity in Uranium During Thermal Cycling

During rapid thermal cycling tests, in which the duration of each cycle was 50 sec, considerable changes occurred in uranium. The extent of the changes depended on the temperature interval of each cycle. Thermal cycling in the α-range to an upper temperature of 550-600°C caused a directional deformation in textured uranium containing about 0-1 per cent carbon. The growth was accompanied by the development of porosity, and a consequent fall in density. After 5000 cycles, the density decreased by 8 per cent. Thermal cycling through both the α-β and β-γ phase transformations caused a rapid change in the shape of the uranium specimens, and rapid development of porosity. The drop in density, after 1000 such cycles, was 30 per cent.