Kinetics of Structural Changes during Beta Transformation of Uranium

When uranium with preferred orientation is heat treated at low beta phase temperatures and cooled in air, grain coarsening proceeds at a more rapid rate than the loss of preferred orientation. Quenching into water from the beta temperature increases the rate of loss of preferred orientation and refines the grain size. To account for these effects, it is postulated that the transformation from the highly oriented alpha phase to the beta phase is incomplete in short times at low beta phase temperatures, and that during cooling the residual alpha grains serve as centers for retransformation to an oriented, large-grained alpha phase. Quenching increases nucleation from the beta phase, and results in a structure that is finer grained and more randomly oriented.