Phase Stability in U-6Nb Alloy Doped with Ti from the First Principles Theory

Abstract

First-principles calculations within the density-functional-theory (DFT) approach are conducted in order to explore and explain the effect of small amounts of titanium on phase stability in the U-6Nb alloy. During rapid quenching from high to room temperature, metastable phases α′ (orthorhombic), α″ (monoclinic), and γ0 (tetragonal) can form, depending on Nb concentration. Important mechanical properties depend on the crystal structure and, therefore, an understanding of the effect of impurities on phase stability is essential. Insights on this issue are obtained from quantum-mechanical DFT calculations. The DFT framework does not rely on any material-specific assumptions and is therefore ideal for an unbiased investigation of the U-Nb system.

Structural, Electronic, and Mechanical Properties of Ag‐Cu‐Ga Intermetallic Compounds: First‐Principles Calculations

“…The Cambridge Sequential Total Energy Package(CASTEP) [13,14] module in Materials studio software is applied to this work. Ultra-soft pseudopotential (USPP) [15] is used to simulate the interaction between valence electrons and ions.…”

Solid-state phase transitions of two quaternary metallic fuel alloys (U-2.5Mo-2.5Ti-5.0Zr and U-1.5Mo-1.5Ti-7.0Zr in wt. %)

“…It is worth mentioning that there are different variants of -U and -U phases that can exist in a uranium alloy (e.g., ', '',  0 ,  s etc.) [18,19,20]. These phases are metastable and may be present when quenching the alloy from high temperature.…”

“…In uranium alloys, the variants of -U are  s and  0 phases [20]. The  s phase might be interpreted as a doubled BCC cell in two directions due to periodic displacement of central atoms in the unit cells [20,32]. Its XRD spectrum is similar to that of -U with the doubled lattice constant [32].…”

Mechanical and Thermal Properties for Uranium and U–6Nb Alloy from First-Principles Theory

“…From a modeling standpoint, there are fewer studies on the uranium-niobium system, but there are some recent phenomenological works reported [25,[27][28][29]. Uranium-niobium has also been investigated from first-principles electronic structure theory [30][31][32][33]. However, no theoretical or experimental data on elastic properties are found in the literature, even though they are central for understanding the mechanical behavior and the SME of the U-Nb alloys.…”