Eutectoid phase transformation in U-Mo-X alloys

Abstract

U-Mo based alloys undergo eutectoid phase transformation where high temperature γ-U decomposes into α-U and U2Mo phases. In the present study, eutectoid decomposition of γ-U phase into α-U and γ’-U2Mo phases in three U-9 Mo, U-8Mo-1V and U-8Mo-1Zr alloys was examined. By carrying out detailed crystallographic analysis of the eutectoidally decomposed products of the U-9Mo alloy, orientation relationships between the parent and product phases were determined. Using the orientation relationship, lattice correspondence among the parent and product phases has been worked out. This lattice correspondence has shown that the product lattices could be derived from the (110) planes of the parent γ-phase wherein the (110) plane of the γ-phase can be converted into the (001) plane of the α-phase and (110) or (103) planes of the γ’-phase. However, during transformation, occurrence of strains within lattice could be one factor through which the kinetics of the phase transformation or morphology of daughter products could be controlled. Based on this idea, ternary alloy additions with different sizes of the solute atoms (Zr or V) have been carried out. This allowed us to manipulate the strain associated with the transformation which was reflected in terms of changes in the width of product phase lamellae.