Straightforward understanding of the structures of metastable alpha '' and possible ordered phases in uranium-niobium alloys from crystallographic simulation

摘要

Crystallographic simulation is carried out in the present work to understand the respective structure of metastable alpha '' and possible ordered phases, which could be the prerequisite for revealing the low-temperature aging mechanism underlying the alpha '' phase in U-Nb alloys. The space group of No. 11 with C-type lattice is found to describe the structure of alpha '' phase in a straightforward way, avoiding the mistaken or indirect indexation and analysis of structural data. The obtained theoretical diffraction pattern of alpha '' phase shows clearly the phenomenon of peak splitting, in which the Bragg positions also agree well with the experimental observation. Additional peaks are observed at the low diffraction angles for the possible ordered phases in U-Nb alloys through simulation on the proposed two types of structures, which need to be carefully detected by the uniting of multiprobe diffraction. The correlation between ordered structures and stress-strain response is also deduced and discussed. The present work would provide some enlighten to the integrity of the phase diagram and the understanding of low-temperature aging mechanism in UeNb alloys. (C) 2015 Elsevier B.V. All rights reserved.