Study on the Role of Second Phase Particles in Hydrogen Uptake Behavior of Zirconium Alloys

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.

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Effect of Bi Addition on the Corrosion Behavior of Zirconium Alloys

Volume 1: Plant Operations, Maintenance, Engineering, Modifications, Life Cycle and Balance of Plant; Nuclear Fuel and Materials; Radiation Protection and Nuclear Technology Applications ◽

10.1115/icone21-15460 ◽

2013 ◽

Cited By ~ 1

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.

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Role of Second-Phase Particles on In Situ Deformation of an AZ80 Mg Alloy

Applications of Microscopy in Materials and Life Sciences - Springer Proceedings in Materials ◽

10.1007/978-981-16-2982-2_6 ◽

2021 ◽

pp. 55-64

Author(s):

R. Sarvesha ◽

W. Alam ◽

J. Jain ◽

S. S. Singh

Keyword(s):

Mg Alloy ◽

Second Phase ◽

Second Phase Particles ◽

In Situ Deformation

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Role of second-phase particles in the microstructural evolution and mechanical properties of extruded Mg-Gd-Y-Ag-Zr alloys

Materials Today Communications ◽

10.1016/j.mtcomm.2020.100956 ◽

2020 ◽

Vol 24 ◽

pp. 100956

Author(s):

Fan Zhang ◽

Yafei Wang ◽

Yunbiao Duan ◽

Kaijun Wang ◽

Yutian Wang ◽

...

Keyword(s):

Mechanical Properties ◽

Microstructural Evolution ◽

Second Phase ◽

Second Phase Particles ◽

Zr Alloys

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

Metals ◽

10.3390/met8100759 ◽

2018 ◽

Vol 8 (10) ◽

pp. 759 ◽

Cited By ~ 6

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.

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