THE TRANSFORMATION BEHAVIOUR OF SOME DILUTE URANIUM ALLOYS

Metallographic and dilatometric studies of the heat treatment behavior of technical uranium and certain alloys of interest for use in natural-uranium fuelled reactors are described. The micro-structure and secondary phases present in high purity and technical purity uranium are first discussed and the time- temperature-transformation data presented. Results on binary alloys comprising U/ Al, U/Cr, U/Fe, U/Mo, U/Nb, U/Ti, U/V, and U/Zr, containing up to about 2 at.% of the alloying element, are described. Cr, Fe, and Zr were found to be the most effective grain refining agents. Al and V were satisfactory under some conditions whereas Mo, Nb, and Ti were ineffective. The grain-size results together with the time-temperaturetransformation curves indicated that grain refinement is associated with depression of the temperature of transformation on heat treatment, the extent of this depression for a given cooling rate being dependent on the alloy content. In practice it was found that alloys such as U/ Zr and U/Fe responded to water quenching treatments, and optimum refinement of others (e.k., U/Cr) resulted from isothermal treatment at 500 to 600 deg C. (auth