Understanding Radiation Effects in Friction Stir Welded MA956 using Ion Irradiation and a Rate Theory Model

2022 ◽  
pp. 153530
Author(s):  
E. Getto ◽  
N. Nathan ◽  
J. McMahan ◽  
S. Taller ◽  
B. Baker
Keyword(s):  
Radiation Effects ◽  
Ion Irradiation ◽  
Theory Model ◽  
Rate Theory ◽  
Friction Stir

A Phenomenological Model for the Effect of Nanocrystalline Microstructure on Irradiation-Induced Amorphization In U3Si

1994 ◽  
Vol 373 ◽  
Author(s):  
J. Rest
Keyword(s):  
Critical Temperature ◽  
Grain Boundaries ◽  
Ion Irradiation ◽  
Theory Model ◽  
Rate Theory ◽  
Two Phase ◽  
Thermal Crystallization ◽  
Acoustic Shock Wave ◽  
Radiation Induced ◽  
Nanocrystalline Microstructure

AbstractA rate theory model is formulated wherein amorphous clusters are formed by a damage event. These clusters are considered centers of expansion (CEs), or excess-free-volume zones. Simultaneously, centers of compression (CCs) are created in the material. The CCs are local regions of increased density that travel through the material as an elastic (e.g., acoustic) shock wave. The CEs can be annihilated upon contact with a sufficient number of CCs, to form either a crystallized region indistinguishable from the host material, or a region with a slight disorientation (recrystallized grain). Recrystallized grains grow by the accumulation of additional CCs.Preirradiation of U3Si above the critical temperature for amorphization results in the formation of nanometer-size grains. In addition, subsequent reirradiation of these samples in the same ion flux at temperatures below the critical temperature shows that the material has developed a resistance to radiation-induced amorphization (i.e., a higher dose is needed to amorphize preirradiated samples than those that have not been preirradiated). In the model, it is assumed that grain boundaries act as effective sinks for defects, and that enhanced defect annihilation is responsible for retarding amorphization below the critical temperature by, for example, preventing a buildup of vacancies adjacent to the grain boundaries. The calculations have been validated against data from ion-irradiation experiments with U3Si. For appropriate values of the activation energy of thermal crystallization, the model predicts the evolution of a two phase microstructure consisting of nanocrystalline grains and amorphous clusters.

scholarly journals Radiation Effects in Amorphous Metallic Alloys as Revealed by Mössbauer Spectrometry: Part II. Ion Irradiation

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1309
Author(s):  
Marcel Miglierini
Keyword(s):  
Heavy Ions ◽  
Radiation Effects ◽  
Ion Irradiation ◽  
Active Regions ◽  
Mössbauer Spectrometry ◽  
Metallic Alloys ◽  
Conversion Electrons ◽  
Amorphous Metallic Alloys ◽  
Mossbauer Spectrometry ◽  
Light Ions

Due to their excellent magnetic properties, amorphous metallic alloys (AMAs) are considered for the construction of magnetic cores of radio-frequency cavities in accelerators. Here, they might be exposed to ion bombardment. The influence of irradiation by both light and heavy ions featuring low and high energies, respectively, is followed by the techniques of 57Fe Mössbauer spectrometry. Modifications of surface layers in selected Fe-containing AMAs after ion irradiation are unveiled by detection of conversion electrons and photons of characteristic radiation whereas those in their bulk are derived from standard transmission spectra. Rearrangement of microstructure which favors the formation of magnetically active regions, is observed in surface regions bombarded by light ions. Heavy ions caused pronounced effects in the orientation of net magnetization of the irradiated samples. No measurable impact upon short-range order arrangement was observed. Part I of this paper is devoted to radiation effects in Fe-based AMAs induced by neutron irradiation.

Microstructure-dependent rate theory model of defect segregation and phase stability in irradiated polycrystalline LiAlO2

2021 ◽  
Author(s):  
Shenyang HU ◽  
Yulan Li ◽  
Shunli Shang ◽  
Zi-Kui Liu ◽  
Douglas Burkes ◽  
...  
Keyword(s):  
Phase Stability ◽  
Release Kinetics ◽  
Field Method ◽  
Thermomechanical Properties ◽  
Theory Model ◽  
Phase Field Method ◽  
Rate Theory ◽  
Kinetic Properties ◽  
Burnable Absorber ◽  
Defect Mobility

Abstract Gamma lithium aluminate (LiAlO2) is a breeder material for tritium and is one of key components in a tritium-producing burnable absorber rod (TPBAR). Dissolution and precipitation of second phases such as LiAl5O8 and voids are observed in irradiated LiAlO2. Such microstructure changes cause the degradation of thermomechanical properties of LiAlO2 and affect tritium retention and release kinetics, and hence, the TPBAR performance. In this work, a microstructure-dependent model of radiation-induced segregation (RIS) has been developed for investigating the accumulation of species and phase stability in polycrystalline LiAlO2 structures under irradiation. Three sublattices (i.e., [Li, Al, V]I [O, Vo]II [Lii, Ali, Oi, Vi]III), and concentrations of six diffusive species (i.e., Li; vacancy of Li or Al at [Li, Al, V]I sublattice, O vacancy at [O, Vo]II sublattice, and Li, Al and O interstitials at [Lii, Ali, Oi, Vi]III interstitial sublattices; are used to describe spatial and temporal distributions of defects and chemistry. Microstructure-dependent thermodynamic and kinetic properties including the generation, reaction, and chemical potentials of defects and defect mobility are taken into account in the model. The parametric studies demonstrated the capability of the developed RIS model to assess the effect of thermodynamic and kinetic properties of defects on the segregation and depletion of species in polycrystalline structures and to explain the phase stability observed in irradiated LiAlO2 samples. The developed RIS model will be extended to study the precipitation of LiAl5O8 and voids and tritium retention by integrating the phase-field method.

Rate Theory for Dislocation Loops Evolution in AL-6XN Austenitic Stainless Steel under Proton Irradiation

2018 ◽  
Vol 913 ◽  
pp. 237-246 ◽  
Author(s):  
Yan Xia Yu ◽  
Li Ping Guo ◽  
Zheng Yu Shen ◽  
Yun Xiang Long ◽  
Zhong Cheng Zheng ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Supercritical Water ◽  
Proton Irradiation ◽  
Theory Model ◽  
Average Density ◽  
Rate Theory ◽  
Dislocation Loops ◽  
Average Size ◽  
Supercritical Water Cooled Reactor

The average size and density evolution of dislocation loops in AL-6XN austenitic stainless steel, a candidate fuel cladding material for supercritical water-cooled reactor, under proton irradiation were simulated through a rate theory model. The simulation results exhibit relatively good agreement with the experimental results at 563 K. The size and density of defect clusters are calculated under irradiation temperature between 550 K and 900 K and irradiation doses up to 15 dpa which satisfies the working condition in supercritical water-cooled reactor. The fast nucleation between self-interstitials happens at the initial stage of irradiation. The average size of dislocation loops increases while the average density of these loops reduces with the increasing temperature, and the average density approaches to a constant when irradiated at higher irradiation doses. The mechanism is discussed based on the variation of rate constants of defect reactions and the variation of the diffusion coefficients of interstitials and dislocation loops with dose and temperature.

Radiation-Induced Minor Element Segregation at Austenitic Stainless Steel Grain Boundaries

1996 ◽  
Vol 439 ◽  
Author(s):  
E. P. Simonen ◽  
S. M. Bruemmer
Keyword(s):  
Grain Boundaries ◽  
Neutron Irradiation ◽  
Ion Irradiation ◽  
Austenitic Stainless Steels ◽  
Minor Element ◽  
High Rate ◽  
Rate Theory ◽  
Minor Elements ◽  
Radiation Induced ◽  
Irradiation Behavior

AbstractMeasurement of minor element compositions at irradiated grain boundaries in austenitic stainless steels indicates that Si is the only element that significantly responds to radiation-induced segregation. Other minor elements, such as P or S, do not exhibit elevated grain boundary concentrations after irradiation. A rate theory evaluation of segregation is in accord with ioninduced Si enrichment, but reveals complexities in the interpretation of extrapolating behavior from ion-irradiation to neutron-irradiation behavior. The model calibrated to measured high-rate, ioninduced segregation greatly overestimates measured low-rate, neutron-irradiation segregation of Si.

Rectification of whole cell cystic fibrosis transmembrane conductance regulator chloride current

1995 ◽  
Vol 268 (3) ◽  
pp. C636-C646 ◽  
Author(s):  
J. L. Overholt ◽  
A. Saulino ◽  
M. L. Drumm ◽  
R. D. Harvey
Keyword(s):  
Cystic Fibrosis ◽  
Theory Model ◽  
Rate Theory ◽  
Dependent Manner ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Concentration Dependent Manner ◽  
Whole Cell ◽  
Multiple Binding Sites ◽  
Cystic Fibrosis Transmembrane

Whole cell epithelial cystic fibrosis transmembrane conductance regulator (CFTR) Cl- currents exhibited a linear current-voltage (I-V) relationship with high symmetrical transmembrane Cl- concentrations. However, when intracellular Cl- (Cli-) was reduced by replacement with glutamate, I-V relationships were outwardly rectifying. Rectification was not affected by reducing extracellular Cl- to eliminate or reverse the gradient, indicating that rectification is not a function of the Cl- gradient. Rectification was affected by Cli- in a concentration-dependent manner, and it was weaker when Cli- was reduced by replacement with sucrose. These characteristics are identical to those of the cardiac isoform of CFTR, and the experimental data could be simulated by an Eyring rate theory model assuming that permeating anions interact at a single binding site within the channel pore. No evidence was found for multiple binding sites. These results indicate that rectification is a function of the concentration and permeability of the anions inside the cell. It is concluded that rectification of CFTR Cl- current is a property of ion channel permeation that would occur under physiological conditions and that permeation of the epithelial and cardiac isoforms of CFTR is identical.

Rate Theory Modeling of Irradiation-induced Phosphorus Segregation in FCC nickel Using First Principles Calculations

2008 ◽  
Vol 1125 ◽  
Author(s):  
Ken-ichi Ebihara ◽  
Masatake Yamaguchi ◽  
Hideo Kaburaki ◽  
Yutaka Nishiyama
Keyword(s):  
First Principles ◽  
Interstitial Site ◽  
Theory Model ◽  
First Principles Calculation ◽  
Rate Theory ◽  
Vacancy Mechanism ◽  
First Principles Calculations ◽  
Phosphorus Segregation ◽  
Octahedral Interstitial Site ◽  
P Distribution

ABSTRACTWe have evaluated phosphorus (P) segregation in ion-irradiated nickel (Ni) by the rate theory model incorporating the results of first principles calculations. We find from our first principles calculation that the transport of P via the rotation mode of a mixed-dumbbell is unlikely to occur, and the transport coefficient of phosphorus by the vacancy mechanism is much larger than that reported previously. On the basis of our first principles results, we have also proposed to include the effect of free migration of P via the octahedral interstitial site of FCC Ni crystal in the rate theory model. With all these renewed parameters, we have successfully obtained the P distribution in irradiated Ni, which is very close to experiment, by adjusting the effect of P transport by the vacancy mechanism.

Radiation Effects in Nonmetals: Amorphization, Phase Decomposition, and Nanoparticles

1998 ◽  
Vol 540 ◽  
Author(s):  
A. Meldrum ◽  
L.A. Boatner ◽  
C.W. White ◽  
D.O. Henderson
Keyword(s):  
Ion Implantation ◽  
Electron Irradiation ◽  
Radiation Effects ◽  
Elevated Temperatures ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Semiconductor Nanocrystals ◽  
Heavy Ion ◽  
Fused Silica ◽  
Near Surface

AbstractRadiation effects in nonmetals have been studied for well over a century by geologists, mineralogists, physicists, and materials scientists. The present work focuses on recent results of investigations of the ion-beam-induced amorphization of the ABO4 compounds – including the orthophosphates (LnPO4; Ln = lanthanides) and the orthosilicates: zircon (ZrSiO4), hafnon (HfSiO4), and thorite (ThSiO4). In the case of the orthosilicates, heavy-ion irradiation at elevated temperatures causes the precipitation of a nanocrystalline metal oxide. Electron irradiation effects in these amorphized insulating ceramics can produce localized recrystallization on a nanometer scale. Similar electron irradiation techniques were used to nucleate monodispersed compound semiconductor nanocrystals formed by ion implantation of the elemental components into fused silica. Methods for the formation of novel structural relationships between embedded nanocrystals and their hosts have been developed and the results presented here demonstrate the general flexibility of ion implantation and irradiation techniques for producing unique near-surface microstructures in ion-implanted host materials.

Sign in / Sign up

Export Citation Format

Share Document