As an important material, uranium-niobium alloy is widely used in the field of nuclear industry because of its high density, excellent corrosion resistance and good mechanical properties. Uranium-niobium alloy is significantly affected by composition and heat treatment process, showing complex phase transition and microstructure characteristics, which makes uranium-niobium alloy corrosion resistance and mechanical properties can be regulated in a wide range. In this paper, according to the main line of "composition/process - structure - property", the research progress of u-NB alloy structure and property control in recent years is reviewed. It is considered that low temperature aging mechanism and impurity control technology are still the key issues in the research of u-NB binary alloy. The emergence of high throughput design, preparation and characterization methods has brought new opportunities and challenges for the future study of structure and property regulation of uranium-niobium multi-element alloys.
When the content of niobium in uranium-niobium alloy is 4.0wt. %~6.9wt. %(9.6at. %~16.0at. %), the α "phase uranium-niobium alloy formed by high temperature quenching has almost the lowest symmetry in crystallography, but its plasticity is comparable to that of stainless steel with high symmetry structure materials. And there are double yield and shape memory effects in the deformation process. In addition, due to the uniform distribution of Niobium in the matrix, α "phase u-Nb alloy also exhibits excellent corrosion resistance. All these make α -phase uranium-niobium alloys the focus of researchers [5-8]. The strength of α "phase uranium-niobium alloy is low, but the yield strength of the alloy can be significantly improved by aging treatment on the basis of ensuring that the plasticity of the alloy is basically unchanged. Therefore, the mechanism of α "phase transition during aging process has been deeply discussed. Hackenberg summarized the phase transition mechanism at different temperatures: At high temperature aging (400~650 ℃), the phase transition is typical diffusional nucleation and growth, including discontinuous precipitation and discontinuous coarsening. The redistribution of Niobium occurs during medium temperature aging (250~400 ℃). At low temperature aging (≤250 ℃), no obvious change of matrix structure was observed. The low temperature aging process of α "phase uranium-niobium alloy has aroused extensive interest of researchers because the microstructure changes are not obvious but the mechanical properties change significantly.
