Local Atomic Structure in Uranium-Niobium Shape Memory Alloys

摘要

Uranium is used as a reactor fuel and in many other applications because of its high density and nuclear features. However, to improve its corrosion resistance and ductility, it has been necessary to alloy it with other metallic elements such as Mo, Nb, Ti, Zr.' This work concerns UNb alloys that exhibit the shape memory effect (SME), which occurs for Nb concentrations close to the monotectoid concentration. The SME seems to be strongly correlated to the martensitic transformations occurring in these alloys. There is an extensive literature describing the different phases in the UNb system, the structural relationships between them, and their stages of appearance. Moreover, it is apparent that the solute plays an important role in defining the type of stabilized phase as a function of solute concentration. Thus, further investigations using different approaches should be pursued to better understand the structure of these alloys, including the short-range as well as long-range order and the associations between them. An important objective in such studies would be to elucidate the role of the Nb solute in the phase stability and SME.