Effect of β phase, precipitate and Nb-concentration in matrix on corrosion and oxide characteristics of Zr–xNb alloys

Corrosion of Zr-1Nb and Zr-2.5Nb in 0.1 M LiOH at 343°C

“…The '-martensitic structures having niobium supersaturation in the matrix show poor corrosion resistance with the highest corrosion rates [Kim et al, 2004, Choo et al, 1994. Moreover, it can be found in the literature that ageing treatments below the monotectoid temperature of 610°C improve the corrosion resistance of alloys with both g '-martensitic and ( -Zr+ -Zr) structures [Jeong et al, 2003, Kim et al, 2004, Choo et al, 1994. It is not clear yet if the beneficial effect of ageing is due to the precipitation of small particles of equilibrium -Nb phase (80 to 85% Nb) [Choo et al, 1994, Kim et al, (2005 or to the presence of a α-Zr matrix with a niobium content close to the terminal solubility.…”

“…Pre-transition oxides (∆w ~ 20 mg/dm 2 ) formed in water at 360°C in Zr-xNb alloys (x = 1 to 5 %) [Jeong et al, 2003, Kim et al, 2004 were reported to have a higher volume fraction of protective tetragonal ZrO 2 (present in the barrier layer) in aged materials than in non-aged ones. Jeong et al (2003) observed that the -Nb particles remained amorphous and partially oxidized in the columnar monoclinic ZrO 2 of aged alloys, while in non-aged materials the -Zr phase was fully oxidized and developed a micro-equiaxed oxide structure. According to these authors, the -Zr phase would accelerate the transformation from the columnar oxide to the equiaxed one (which is detrimental to the corrosion resistance) at the interface between -Zr and surrounding oxide.…”

“…Moreover, the high temperature corrosion of Zr-Nb alloys strongly depends on the microstructure. This dependence has been widely studied in water [Jeong et al, 2003, Kim et al, 2004 and in diluted LiOH solutions [Choo et al, 1994; but studies concerning Zr-Nb alloys and the influence of microstructure in concentrated LiOH solutions have not been reported.…”

Solubility in Zr-Nb alloys from first-principles

“…Under irradiation, one observes a partial amorphization and dissolution of these Laves phases, which is common to all zirconium alloys, and, more specifically for Zr-Nb alloys, the formation of very fine Nb-rich β precipitates leading to a decrease of the Nb content in the α matrix [18,[21][22][23][24][25][26][27]. Since the mechanical properties of Zr-Nb alloys [28][29][30], as well as their corrosion resistance [5,31,32] and their magnetic susceptibility [7,8], are strongly dependent on the precipitate microstructure and on the solute content of the α matrix, knowledge of the thermodynamic properties of the system as well as the resulting phase boundaries is of critical technological interest.…”

Propiedades de superficies de Zr hexagonal y ZrO2 tetragonal de bajo índice a partir de cálculos DFT

“…La estabilidad relativa de ambos polimorfismos de composición ZrO 2 ha sido correctamente predicha por métodos basados en la Teoría de la Funcional Densidad (DFT, [1]) ( [1][2][3][4]). Una investigación de la superficie metálica fue presentada por YAMAMOTO et al [1] quienes usaron modelos de O/Zr para demostrar por primeros principios que el alojamiento de oxígeno en los sitios octaedrales entre la segunda y tercera capa de circonio está energéticamente favorecido.…”