scholarly journals Homogenization and Growth Behavior of Second-Phase Particles in a Deformed Zr–Sn–Nb–Fe–Cu–Si–O Alloy

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 759 ◽  
Author(s):  
Liang-Yu Chen ◽  
Peng Sang ◽  
Lina Zhang ◽  
Dongpo Song ◽  
Yan-Qiu Chu ◽  
...  
Keyword(s):  
Ostwald Ripening ◽  
Short Circuit ◽  
Zirconium Alloys ◽  
Lattice Diffusion ◽  
Growth Behavior ◽  
Homogeneous Distribution ◽  
Second Phase ◽  
Deformation Degree ◽  
Linear Distribution ◽  
Second Phase Particles

Homogeneous distribution of fine second-phase particles (SPPs) fabricated by cycles of deformation and annealing in zirconium alloys is a critical consideration for the corrosion resistance of fuel claddings. Different deformation degrees of zirconium alloys would result in distinctive microstructures, leading to a distinct growth of SPPs during subsequent annealing. Unfortunately, the homogenization and growth behavior of SPPs in deformed zirconium alloys have not been well studied. In this work, a β-quenched Zr–Sn–Nb–Fe–Cu–Si–O alloy was rolled and annealed at 580 °C or 680 °C. The morphologies, distributions, and sizes of SPPs resulting from the different processing procedures were investigated. A linear distribution of SPPs is found in the β-quenched sample. Afterward, SPPs grow and are randomly distributed during heat treatment as the deformation degree or annealing time (or temperature) increases. The homogenization and growth of SPPs are attributed to the Ostwald ripening mechanism that is governed by lattice diffusion and short-circuit diffusion. The sample with a higher deformation degree is speculated to have a larger number of defects that provide more shortcuts for the mass transfer of SPPs, thereby facilitating a homogeneous distribution of fine SPPs during annealing.

scholarly journals Evidence of hydrogen trapping at second phase particles in zirconium alloys

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christopher Jones ◽  
Vidur Tuli ◽  
Zaheen Shah ◽  
Mhairi Gass ◽  
Patrick A. Burr ◽  
...  
Keyword(s):  
Density Functional ◽  
Secondary Ion Mass Spectrometry ◽  
Zirconium Alloys ◽  
Nuclear Industry ◽  
Second Phase ◽  
Hydrogen Trapping ◽  
Functional Theory ◽  
Second Phase Particles ◽  
Hydrogen Isotope Ratios ◽  
Dft Modelling

AbstractZirconium alloys are used in safety–critical roles in the nuclear industry and their degradation due to ingress of hydrogen in service is a concern. In this work experimental evidence, supported by density functional theory modelling, shows that the α-Zr matrix surrounding second phase particles acts as a trapping site for hydrogen, which has not been previously reported in zirconium. This is unaccounted for in current models of hydrogen behaviour in Zr alloys and as such could impact development of these models. Zircaloy-2 and Zircaloy-4 samples were corroded at 350 °C in simulated pressurised water reactor coolant before being isotopically spiked with 2H2O in a second autoclave step. The distribution of 2H, Fe and Cr was characterised using nanoscale secondary ion mass spectrometry (NanoSIMS) and high-resolution energy dispersive X-ray spectroscopy. 2H− was found to be concentrated around second phase particles in the α-Zr lattice with peak hydrogen isotope ratios of 2H/1H = 0.018–0.082. DFT modelling confirms that the hydrogen thermodynamically favours sitting in the surrounding zirconium matrix rather than within the second phase particles. Knowledge of this trapping mechanism will inform the development of current understanding of zirconium alloy degradation through-life.

Effect of Bi Addition on the Corrosion Behavior of Zirconium Alloys

2013 ◽  
Author(s):  
M. Y. Yao ◽  
B. X. Zhou ◽  
Q. Li ◽  
W. P. Zhang ◽  
L. Zhu ◽  
...  
Keyword(s):  
Solid Solution ◽  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Mass Fraction ◽  
Zirconium Alloys ◽  
Deionized Water ◽  
Second Phase ◽  
Micro Structure ◽  
Second Phase Particles ◽  
Structure Observation

In order to investigate systematically the effect of Bi addition on the corrosion resistance of zirconium alloys, different zirconium-based alloys, including Zr-4 (Zr-1.5Sn-0.2Fe-0.1Cr), S5 (Zr-0.8Sn-0.35Nb-0.4Fe-0.1Cr), T5 (Zr-0.7Sn-1.0Nb-0.3Fe-0.1Cr) and Zr-1Nb, were adopted to prepare the zirconium alloys containing Bi of 0∼0.5% in mass fraction. These alloys were denoted as Zr-4+xBi, S5+xBi, T5+xBi and Zr-1Nb+xBi, respectively. The corrosion behavior of these specimens was investigated by autoclave testing in lithiated water with 0.01 M LiOH or deionized water at 360°C/18.6 MPa and in superheated steam at 400 °C/10.3 MPa. The micro structure of the alloys was examined by TEM and the second phase particles (SPPs) were analyzed by EDS. Micro structure observation shows that the addition of Bi promotes the precipitation of Sn as second phase particles (SPPs) because Sn is in solid solution in α-Zr matrix in Zr-4, S5 and T5 alloys. The concentration of Bi dissolved in α-Zr matrix increase with the increase of Nb in the alloys, and the excess Bi precipitates as Bi-containing SPPs. The corrosion results show that the effect of Bi addition on the corrosion behavior of different zirconium-based alloys is very complicated, depending on their compositions and corrosion conditions. In the case of higher Bi concentration in α-Zr, the zirconium alloys exhibit better corrosion resistance. However, in the case of precipitation of Bi-containing SPPs, the corrosion resistance gets worse. This indicates that the solid solution of Bi in α-Zr matrix can improve the corrosion resistance, while the precipitation of the Bi-containing SPPs is harmful to the corrosion resistance.

Observation of second-phase particles in bulk zirconium alloys using synchrotron radiation

2001 ◽  
Vol 294 (3) ◽  
pp. 299-304 ◽  
Author(s):  
Kenneth T. Erwin ◽  
Olivier Delaire ◽  
Arthur T. Motta ◽  
Yong S. Chu ◽  
Derrick C. Mancini ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Zirconium Alloys ◽  
Second Phase ◽  
Second Phase Particles

Stabilizing the nanostructure in ball-milled iron alloys through the addition of oxide precipitates

1996 ◽  
Vol 54 ◽  
pp. 226-227
Author(s):  
C.P. Doğan ◽  
J.C. Rawers
Keyword(s):  
Thermal Stability ◽  
Elevated Temperatures ◽  
Effective Means ◽  
High Energy ◽  
Homogeneous Distribution ◽  
Second Phase ◽  
Boundary Area ◽  
Second Phase Particles ◽  
Energy Ball ◽  
Processing Techniques

High-energy ball milling has proved to be an effective means of producing nanostructured metal alloys from elemental powders. Interest has focussed on this processing method because of its potential to form metastable compositions with a combination of properties not attainable by more conventional processing techniques. Consolidation of the resulting powders into commercially-viable solids has proven difficult, however. Because of the metastable nature of the compositions formed and the extremely high boundary area that makes up the nanostructure, these materials are very susceptible to exposure to elevated temperatures. Since most conventional consolidation techniques involve high temperatures, the nanostructure within the powders is typically lost during this processing step. Thus, a reliable means of enhancing the thermal stability of these materials, allowing economical consolidation, is clearly needed.One possible method to enhance thermal stability is to introduce a homogeneous distribution of stable second phase particles that will pin the grain boundaries, allowing retention of the nanostructure at temperatures high enough for effective consolidation.

Growth behavior study of second phase particles in a Zr–Sn–Nb–Fe–Cr–Cu alloy

2012 ◽  
Vol 423 (1-3) ◽  
pp. 127-131 ◽  
Author(s):  
B.F. Luan ◽  
L.J. Chai ◽  
J.W. Chen ◽  
M. Zhang ◽  
Q. Liu
Keyword(s):  
Growth Behavior ◽  
Second Phase ◽  
Cu Alloy ◽  
Behavior Study ◽  
Second Phase Particles

scholarly journals Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 850 ◽  
Author(s):  
Lina Zhang ◽  
Liang-Yu Chen ◽  
Cuihua Zhao ◽  
Yujing Liu ◽  
Lai-Chang Zhang
Keyword(s):  
Corrosion Resistance ◽  
Weight Gain ◽  
Oxide Film ◽  
Corrosion Behavior ◽  
Diffusion Coefficients ◽  
Oxygen Diffusion ◽  
Short Circuit ◽  
Oxide Films ◽  
Zirconium Alloys ◽  
Second Phase

The growth of oxide film, which results from the inward oxygen diffusion from a corrosive environment, is a critical consideration for the corrosion resistance of zirconium alloys. This work calculates the oxygen diffusion coefficients in the oxide films formed on zirconium alloys annealed at 400~500 °C and investigates the related corrosion behavior. The annealed samples have a close size for the second-phase particles but a distinctive hardness, indicating the difference in substrate conditions. The weight gain of all samples highly follows parabolic laws. The weight gain of the sample annealed at 400 °C has the fastest increase rate at the very beginning of the corrosion test, but its oxide film has the slowest growth rate as the corrosion proceeds. By contrast, the sample annealed at 500 °C shows the lowest weight gain but the highest corrosion rate constant. Such a corrosion behavior is attributed to the amount of defects existing in the oxide film formed on the annealed samples; fewer defects would provide a lower fraction of short-circuit diffusion in total diffusion, resulting in a lower diffusion coefficient of oxygen in the oxide film, thereby producing better corrosion resistance. This is consistent with the calculated diffusion coefficients of oxygen in the oxide films: 3.252 × 10−11 cm2/s, 3.464 × 10−11 cm2/s and 3.740 × 10−11 cm2/s for the samples annealed at 400 °C, 450 °C, and 500 °C, respectively.

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