Phase boundary of the Zr-rich region in commercial grade Zr–Nb alloys

Analysis of oxidation behavior of the β-Nb phase formed in Zr–1.5Nb alloy by using the HVEM

“…2 shows the ␤-phase which was observed in the zirconium matrix. It is known that the crystal structure of this phase is BCC, and the composition consisted of Nb (∼80 wt.%) and Zr (∼20 wt.%) [14]. A size of this round shaped phase was about 50 nm in diameter and dark contrast was observed in this spherical phase and the composition of this phase (80 at.% Nb) was similar to the previous result [14] from the EDS analysis.…”

“…It is known that the crystal structure of this phase is BCC, and the composition consisted of Nb (∼80 wt.%) and Zr (∼20 wt.%) [14]. A size of this round shaped phase was about 50 nm in diameter and dark contrast was observed in this spherical phase and the composition of this phase (80 at.% Nb) was similar to the previous result [14] from the EDS analysis. To analyze the crystal structure of the observed phases, an image quality enhancement program by the Fast Fourier Transformation (FFT) and Fourier mask filtering tools was used for the high resolution images by using the DigitalMicrograph TM program (DM, Gatan Inc.).…”

“…The quenched ingot was hot-rolled after pre-heating at 580 • C for 10 min and cold-rolled three times to a final thickness of 1 mm. Between the rolling steps, the cold rolled sheet was intermediate-annealed at 580 • C to control the type of the second phase as a ␤-Nb [14]. Specimens for the corrosion test, 25 mm × 15 mm × 1 mm in size, were cut from the sheets, mechanically ground up to 1200 grit SiC paper, and then pickled in a solution of 5 vol.% HF, 45 vol.% HNO3 and 50 vol.% H2O.…”

The role of Fe on the solubility of Nb in α-Zr

“…The room temperature solubility of Nb in a-Zr has been reported as 0.2 wt% [6], 0.8 wt% [7], and 1.1 wt% [6] for Zr-Nb alloys with the major impurities, oxygen and iron, ranging from 1230 to 1400 wt ppm and 550 to 900 wt ppm, respectively. Oxygen stabilizes the a-phase and iron stabilizes the b-phase.…”

Effect of alloying elements (Cu, Fe, and Nb) on the creep properties of Zr alloys

“…Although, the diffusivity of the alloying element in the alpha zirconium was not studied in this work, it is known that niobium has the lowest diffusion rate among the added alloying elements and that iron has a lower diffusion rate than copper in zirconium from previous studies [13,14]. Also, from a study for the solubility limit of an alloying element such as copper [11], iron [12] and niobium [15], it is known that the niobium solubility limit is much higher than the copper or iron solubility limits in alpha zirconium. Therefore, it could be assumed that both factors of a diffusivity and a soluble amount of the alloying elements would control the creep strength of the zirconiumbased alloys.…”