Effect of Formation and Growth of Dislocation Loops and Cavities on Low-Temperature Swelling of Irradiated Uranium-Molybdenum Alloys

1998 ◽  
Vol 540 ◽  
Author(s):  
J. Rest ◽  
G. L. Hofman ◽  
I. I. Konovalov ◽  
A. A. Maslov
Keyword(s):  
Low Temperature ◽  
Rate Theory ◽  
Subgrain Structure ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Molybdenum Alloys ◽  
Fission Gas ◽  
Swelling Mechanism ◽  
Test Reactor ◽  
Low Irradiation

AbstractScanning electron photomicrographs of U–10 wt.% Mo irradiated at low temperature in the Advanced Test Reactor (ATR) to about 40 at.% burnup show the presence of cavities. We have used a rate-theory-based model to investigate the nucleation and growth of cavities during low-temperature irradiation of uranium-molybdenum alloys in the presence of irradiation-induced interstitial-loop formation and growth. Our calculations indicate that the swelling mechanism in the U–10 wt.% Mo alloy at low irradiation temperatures is fission-gas driven. The calculations also indicate that the observed bubbles must be associated with a subgrain structure. Calculated bubble-size-distributions are compared with irradiation data.

Irradiation-Induced Recrystallization of Cellular Dislocation Networks in Uranium-Molybdenum Alloys

2000 ◽  
Vol 650 ◽  
Author(s):  
J. Rest ◽  
G. L. Hofman
Keyword(s):  
Dislocation Structure ◽  
Cell Walls ◽  
Subgrain Boundary ◽  
Lattice Parameter ◽  
Theoretical Description ◽  
Rate Theory ◽  
Dislocation Loops ◽  
Stored Energy ◽  
Molybdenum Alloys ◽  
Structure Calculations

ABSTRACTWe developed a rate-theory-based model to investigate the nucleation and growth of interstitial loops and cavities during low-temperature in-reactor irradiation of uranium-molybdenum alloys. Consolidation of the dislocation structure takes into account the generation of forest dislocations and capture of interstitial dislocation loops. The theoretical description includes stress-induced glide of dislocation loops and accumulation of dislocations on cell walls. The loops accumulate and ultimately evolve into a low-energy cellular dislocation structure. Calculations indicate that nanometer-size bubbles are associated with the walls of the cellular dislocation structure. The accumulation of interstitial loops within the cells and of dislocations on the cell walls leads to increasing values for the rotation (misfit) of the cell wall into a subgrain boundary and a change in the lattice parameter as a function of dose. Subsequently, increasing values for the stored energy in the material are shown to be sufficient for the material to undergo recrystallization. Results of the calculations are compared with SEM photomicrographs of irradiated U- 10Mo, as well as with data from irradiated UO2.

Point Defect Absorption and Dislocation Loop Formation at Grain Boundaries in Hvem-Irradiated Zr and Its Alloys:1. Influence of Solute Addition

1985 ◽  
Vol 43 ◽  
pp. 350-351
Author(s):  
R.A. Herring ◽  
M. Griffiths ◽  
M.H Loretto ◽  
R.E. Smallman
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Point Defect ◽  
Reactor Core ◽  
Solute Concentration ◽  
Nuclear Industry ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Component Material ◽  
Impurity Interaction

Because Zr is used in the nuclear industry to sheath fuel and as structural component material within the reactor core, it is important to understand Zr's point defect properties. In the present work point defect-impurity interaction has been assessed by measuring the influence of grain boundaries on the width of the zone denuded of dislocation loops in a series of irradiated Zr alloys. Electropolished Zr and its alloys have been irradiated using an AEI EM7 HVEM at 1 MeV, ∼675 K and ∼10-6 torr vacuum pressure. During some HVEM irradiations it has been seen that there is a difference in the loop nucleation and growth behaviour adjacent to the grain boundary as compared with the mid-grain region. The width of the region influenced by the presence of the grain boundary should be a function of the irradiation temperature, dose rate, solute concentration and crystallographic orientation.

On the interpretation of dislocation-loop growth during in-situ high-voltage Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 532-533
Author(s):  
E. Holzäpfel ◽  
F. Phillipp ◽  
M. Wilkens
Keyword(s):  
Point Defect ◽  
Rate Equations ◽  
Rate Theory ◽  
Dislocation Loops ◽  
High Voltage Electron Microscopy ◽  
Vacancy Migration ◽  
Voltage Electron ◽  
Reaction Rate Theory ◽  
Defect Reactions

During in-situ radiation damage experiments aiming on the investigation of vacancy-migration properties interstitial-type dislocation loops are used as probes monitoring the development of the point defect concentrations. The temperature dependence of the loop-growth rate v is analyzed in terms of reaction-rate theory yielding information on the vacancy migration enthalpy. The relation between v and the point-defect production rate P provides a critical test of such a treatment since it is sensitive to the defect reactions which are dominant. If mutual recombination of vacancies and interstitials is the dominant reaction, vαP0.5 holds. If, however, annihilation of the defects at unsaturable sinks determines the concentrations, a linear relationship vαP is expected.Detailed studies in pure bcc-metals yielded vαPx with 0.7≾×≾1.0 showing that besides recombination of vacancies and interstitials annihilation at sinks plays an important role in the concentration development which has properly to be incorporated into the rate equations.

Progress of Research on Welding for Molybdenum Alloys

2014 ◽  
Vol 33 (3) ◽  
pp. 193-200 ◽  
Author(s):  
Jiteng Wang ◽  
Juan Wang ◽  
Yajiang Li ◽  
Deshuang Zheng
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Low Temperature ◽  
Welded Joint ◽  
Structural Materials ◽  
Practical Applications ◽  
Traditional Technology ◽  
Molybdenum Alloys ◽  
Resistance To Oxidation ◽  
Temperature Applications

AbstractMolybdenum and molybdenum alloys are considered to be attractive structural materials for high-temperature applications. However, molybdenum alloys are sensitive to gas impurities and have the characteristics of low temperature embrittlement and less resistance to oxidation at elevated temperature. The toughness and strength of welded joint is not easy to be ensured by traditional technology. Recently, many efforts have been made to join molybdenum and its alloys. In this paper, we present the result of investigations on welding methods of molybdenum and its alloys and overview the practical applications in engineering. The key of joining molybdenum alloys is to improve the toughness of welded joint and prevent the generation of pores and cracks.

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.

The Effect of a Thin Sample on the Extended Defect Evolution in Si+ Implanted Si

1997 ◽  
Vol 490 ◽  
Author(s):  
Jing-Hong Li ◽  
Kevin S. Jones
Keyword(s):  
Dislocation Loop ◽  
Ex Situ ◽  
Dissolution Process ◽  
Dislocation Loops ◽  
Loop Formation ◽  
Thin Sample ◽  
Extended Defect ◽  
Defect Evolution ◽  
Annealing Study

ABSTRACTThe annealing kinetics of implant damage in Si+ implanted Si has been investigated using in-situ and ex-situ annealing of transmission electron microscopy (TEM) samples prepared prior to annealing. The defect evolution at 800°C was studied for a Si wafer implanted with Si+ at 100keV to a dose of 2×1014 cm-2. This implant was above the sub-threshold loop formation threshold allowing one to study simultaneously the {311} defect dissolution and dislocation loop nucleation and growth. In order to study the effect on the defect evolution of using a thin sample for an in-situ annealing experiment, a pair of samples, one thick and one thinned into a TEM sample, were annealed in a furnace simultaneously. It was found that the presence of a second surface 2000Å below the implant damage did not affect the extended defect evolution. For the in-situ annealing study it was found that the {311} dissolution process and sub-threshold dislocation loop formation process was not affected by the TEM electron beam at 160kV as long as an 800°C furnace pre-anneal was done prior to in-situ annealing. The dissolution rate of the {311} defects was used to confirm the TEM holder furnace temperature. The results of both the in-situ the {311} defects is released during the 311 dissolution process and 30% comes to reside in dislocation loops. Thus, the loops appear to contain a significant fraction of the total interstitial concentration introduced by the implant.

scholarly journals The type identification of dislocation loops by TEM and the loop formation in pure Fe implanted with H+*

2011 ◽  
Vol 60 (3) ◽  
pp. 036802
Author(s):  
Huang Yi-Na ◽  
Wan Fa-Rong ◽  
Jiao Zhi-Jie
Keyword(s):  
Dislocation Loops ◽  
Loop Formation

scholarly journals Grain-Subgrain Structure and Vacancy-Type Defects in Submicrocrystalline Nickel at Low Temperature Annealing

2015 ◽  
Vol 128 (4) ◽  
pp. 714-718
Author(s):  
P.V. Kuznetsov ◽  
A.M. Lider ◽  
Yu.S. Bordulev ◽  
R.S. Laptev ◽  
T.V. Rakhmatulina ◽  
...  
Keyword(s):  
Low Temperature ◽  
Subgrain Structure ◽  
Low Temperature Annealing

Defect clusters of molybdenum alloys bombarded by HVEM

1978 ◽  
Vol 36 (1) ◽  
pp. 402-403
Author(s):  
N. Igata ◽  
A. Kohyama ◽  
H. Murakami ◽  
K. Itadani ◽  
H. Tsunakawa
Keyword(s):  
Incident Beam ◽  
In Situ Observation ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Voltage Electron ◽  
Molybdenum Alloys ◽  
Damage Process ◽  
Hot Rolled

As a simulation study of heavy radiation damage by neutrons, in-situ observation of damage process in molybdenum alloys was performed by a high voltage electron microscope. The objectives of this study are to clarify the processes of defect cluster nucleation and growth, and the role of alloying elements on these in the temperature range from 300K to 1300K.The used molybdenum alloys were Mo-(150-1000)at.ppm.C, Mo-(0.06-0.6)at.%Nb, MO-0.29at.%Hf, MO-(0.026-26)at.%Re and Mo-0.56at.%Ni. The used materials were electron-beam melted and hot rolled at 200-400°C and annealing was performed in the vacuum of l×l0-7torr. at 1800°C for 1.0 hr. The standard irradiation conditions were as follows,Accelerating voltage: 1250KV, Beam intensity: l-6×l019 e/cm2 sec, Incident beam direction: <100>, g-vector: {110},The density of defect clusters was determined by the thickness gradient method.The logarithmic density of interstitial dislocation loops, logNi, increased with the reciprocal irradiation temperature, 1/T. The relation between logNiand 1/T was divided into two Arrhenius type relations above and below 500K.

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