SOLUTE DISTRIBUTION IN ANNEALED ZIRCALOY-2 AND ZR-2.5NB

Electron probe microanalysis has been applied to determine the tempera ture dependence of solute levels, particularly Fe, in the matrix of la rge-grained, 10-40 mum, Zircaloy-2 (Zy) and Zr-2.5Nb (ZN). The Fe leve ls found in the alpha-phase of both alloys below 600-degrees-C are hig h (approximately 70 at. ppm), in terms of recently published solubilit ies of Fe in alpha-Zr. X-ray mapping shows that Fe, Cr and Ni in Zy ar e concentrated in grain boundary precipitates and that Fe and Nb in ZN are concentrated at the beta (or transformed-beta) regions. The devel opment of the alpha-phase and associated solute-enrichment of the tran sforming beta-phase during annealing are followed as functions of heat treatment by metallography and X-ray mapping.