Radiation-Induced Precipitation in Ti-6A1-4V

1980 ◽  
Vol 38 ◽  
pp. 154-155
Author(s):  
J. E. O'Neal ◽  
S. M. L. Sastry ◽  
J. W. Davis
Keyword(s):  
Dark Field ◽  
Dislocation Loops ◽  
Beta Titanium Alloy ◽  
Defect Clusters ◽  
Weak Beam ◽  
Beta Titanium ◽  
Small Defect ◽  
Radiation Induced ◽  
Vector Orientation ◽  
Defect Microstructures

The radiation-induced defect structure and nonequilibrium phase precipitation were studied in T1-6A1-4V (an alpha-beta titanium alloy), irradiated at 450 ± 30°C in row VII of the EBR-II to a fluence of 3.0 × 1021 neutrons/cm2 (En > 0.1 MeV). The Irradiation-induced defect microstructures were examined using bright-field, conventional dark-field, and weak-beam dark-field techniques. The nature of dislocations and dislocation loops was determined by standard-contrast experiments under two-beam conditions, and the small defect clusters were identified using the line-of-contrast criterion and black-white vector orientation criterion.

The evolution of the microstructure of 600 Mev proton irradiated materials

1990 ◽  
Vol 48 (4) ◽  
pp. 1002-1003
Author(s):  
R. Gotthardt ◽  
A. Horsewell ◽  
F. Paschoud ◽  
S. Proennecke ◽  
M. Victoria
Keyword(s):  
Nuclear Reactions ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Weak Beam ◽  
Stacking Fault Tetrahedra ◽  
Small Defect ◽  
Sufficient Intensity ◽  
Reactor Materials ◽  
Metallic Impurities ◽  
Beam Technique

Fusion reactor materials will be damaged by an intense field of energetic neutrons. There is no neutron source of sufficient intensity at these energies available at present, so the material properties are being correlated with those obtained in irradiation with other irradiation sorces. Irradiation with 600 MeV protons produces both displacement damage and impurities due to nuclear reactions. Helium and hydrogen are produced as gaseous impurities. Other metallic impurities are also created . The main elements of the microstructure observed after irradiation in the PIREX facility, are described in the following paragraphs.A. Defect clusters at low irradiation doses: In specimens irradiated to very low doses (1021-1024 protons.m-2), so that there is no superimposition of contrast, small defect clusters have been observed by the weak beam technique. Detailed analysis of the visible contrast (>0.5 nm diameter) revealed the presence of stacking fault tetrahedra, dislocation loops and a certain number of unidentified clusters . Typical results in Cu and Au are shown in Fig. 1.

Annealing Of Radiation Damage in Tungsten

1970 ◽  
Vol 28 ◽  
pp. 412-413
Author(s):  
Robert C. Rau ◽  
John Moteff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Radiation Damage ◽  
Thermal Annealing ◽  
Neutron Fluence ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Polycrystalline Tungsten ◽  
Transmission Electron ◽  
Radiation Induced

Transmission electron microscopy has been used to study the thermal annealing of radiation induced defect clusters in polycrystalline tungsten. Specimens were taken from cylindrical tensile bars which had been irradiated to a fast (E > 1 MeV) neutron fluence of 4.2 × 1019 n/cm2 at 70°C, annealed for one hour at various temperatures in argon, and tensile tested at 240°C in helium. Foils from both the unstressed button heads and the reduced areas near the fracture were examined.Figure 1 shows typical microstructures in button head foils. In the unannealed condition, Fig. 1(a), a dispersion of fine dot clusters was present. Annealing at 435°C, Fig. 1(b), produced an apparent slight decrease in cluster concentration, but annealing at 740°C, Fig. 1(C), resulted in a noticeable densification of the clusters. Finally, annealing at 900°C and 1040°C, Figs. 1(d) and (e), caused a definite decrease in cluster concentration and led to the formation of resolvable dislocation loops.

scholarly journals Radiation-induced mobility of small defect clusters in covalent materials

2016 ◽  
Vol 94 (2) ◽  
Author(s):  
Hao Jiang ◽  
Li He ◽  
Dane Morgan ◽  
Paul M. Voyles ◽  
Izabela Szlufarska
Keyword(s):  
Defect Clusters ◽  
Small Defect ◽  
Radiation Induced

On Distinguishing between Small Vacancy and Interstitial Dislocation Loops Using a Non-Conventional Weak Beam Dark Field Technique

1975 ◽  
Vol 33 ◽  
pp. 166-167
Author(s):  
Wei-Kuo Wu
Keyword(s):  
Habit Plane ◽  
Dark Field ◽  
Dislocation Loops ◽  
Bright Field ◽  
Burgers Vector ◽  
Field Techniques ◽  
Field Technique ◽  
The Core ◽  
Weak Beam ◽  
Image Width

It is well known that both the burgers vector and the habit plane of dislocation loops are needed in order to determine their type, e.g. vacancy or interstitial. The conventional bright field and dark field techniques give a dislocation image width ⋍300Å or an image shift from the core position even larger than the true size of a small dislocation loop. This makes loop type determination very difficult.In this paper, the newly developed weak beam dark field technique, which decreases the effective extinction distance, ξg, has been used to reduce the dislocation image width (∽1/3 ξg), so that the shape (habit plane) and loop types of small dislocation loops (<500Å) can be determined unambiguously.

Radiation Damage in Vanadium

1968 ◽  
Vol 26 ◽  
pp. 288-289
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd ◽  
John Moteff
Keyword(s):  
Vacuum Annealing ◽  
Neutron Fluence ◽  
Dislocation Loops ◽  
Defect Clusters ◽  
Transmission Electron ◽  
Small Defect ◽  
Cluster Density ◽  
Average Size ◽  
Average Cluster ◽  
Very High

Transmission electron microscopy has been used to study the microstructure of vanadium irradiated at reactor ambient temperature (∼ 70°C) to a fast (E > 1 MeV) neutron fluence of 5 x 1019 n/cm2. Observations were made of the as-irradiated material, and after one-hour vacuum annealing at various temperatures ranging from 330°C to 1175°C.In the as-irradiated condition, shown in Fig. 1, a very high density of small defect clusters was present. These clusters appeared as black dots averaging approximately 25-50 Å in diameter, and were estimated to be present in quantities of 1016 to 1017 per cm3. Post-irradiation annealing caused the clusters to increase in average size and decrease in number, as shown in Figs. 2 and 3, until after the highest temperature anneal, 1175°C, the cluster density was legs than 1014 per cm3 and the average cluster size was approximately 500Å. After annealing at temperatures of 510°C or above, many of the clusters were seen to be resolvable as dislocation loops. Tilting experiments indicated that these loops were probably interstitial in nature.

The Search for Interstitial Dislocation Loops Produced in Displacement Cascades at 20K in Copper

1998 ◽  
Vol 540 ◽  
Author(s):  
M. A. Kirk ◽  
M. L. Jenkins ◽  
H. Fukushima
Keyword(s):  
Low Temperature ◽  
Ion Irradiation ◽  
Dislocation Loops ◽  
Number Of Clusters ◽  
Annealing Experiment ◽  
Defect Clusters ◽  
Displacement Cascades ◽  
Weak Beam

AbstractA low-temperature in situ ion-irradiation and annealing experiment has been performed by TEM in copper. Most defect clusters which persisted through an anneal to 120 K showed no size changes within the resolution (0.5 nm) of a new weak-beam sizing technique. Of 55 defects measured under a range of weakly diffracting conditions, 7 showed measurable size decreases while 3 showed size increases. We argue that these clusters are likely to be of vacancy and interstitial nature, respectively. Also on annealing to 120 K a fraction of about 25% of the clusters formed by irradiation with 600 kV Cu+ ions at 20 K disappeared, while a similar number of clusters appeared in different locations.

Atomistic observation of electron irradiation-induced defects in CeO2

2013 ◽  
Vol 1514 ◽  
pp. 93-98 ◽  
Author(s):  
Seiya Takaki ◽  
Tomokazu Yamamoto ◽  
Masanori Kutsuwada ◽  
Kazuhiro Yasuda ◽  
Syo Matsumura
Keyword(s):  
Electron Irradiation ◽  
Imaging Techniques ◽  
Dark Field ◽  
Dislocation Loops ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Dark Field ◽  
Radiation Induced ◽  
Induced Defects ◽  
Irradiation Induced Defects

ABSTRACTWe have investigated the atomistic structure of radiation-induced defects in CeO2 formed under 200 keV electron irradiation. Dislocation loops on {111} habit planes are observed, and they grow accompanying strong strain-field. Atomic resolution scanning transmission electron microscopy (STEM) observations with high angle annular dark-field (HAADF) and annular bright-field (ABF) imaging techniques showed that no additional Ce layers are inserted at the position of the dislocation loop, and that strong distortion and expansion is induced around the dislocation loops. These results are discussed that dislocation loops formed under electron irradiation are non-stoichiometric defects consist of oxygen interstitials.

scholarly journals Dislocation Loops in Spinel Crystals Irradiated Successively with Deep and Shallow Ion Implants

1993 ◽  
Vol 316 ◽  
Author(s):  
Rebecca X. Ai ◽  
Nicole Bordes ◽  
Elizabeth A. Cooper ◽  
Kurt E. Sickafus ◽  
Rodney C. Ewing ◽  
...  
Keyword(s):  
Irradiation Damage ◽  
Dislocation Loops ◽  
Cross Sectional ◽  
Defect Clusters ◽  
Projected Range ◽  
Weak Beam ◽  
Transmission Electron ◽  
Implant Size ◽  
Oxide Spinel ◽  
Process Measurements

ABSTRACTThis study examines the influence of microstructural defects on irradiation damage accumulation in the oxide spinel. Single crystals of the compound MgAl2O4 with surface normal [111] were irradiated under cryogenic temperature (100°K) either with 50 keV Ne ions (fluence 5.0 × 1012/cm2), 400 keV Ne ions (fluence 6.7 × 1013cm2) or successively with 400 keV Ne ions followed by 50 keV Ne ions. The projected range of 50 keV Ne ions in spinel is ~50 nm (“shallow”) while the projected range of 400 keV Ne ions is ~ 500 nm (“deep”). Transmission electron microscopy (TEM) was used to examine dislocation loops/ defect clusters formed by the implantation process. Measurements of the dislocation loop size were made using weak-beam imaging technique on cross-sectional TEM ion-implanted specimens. Defect clusters were observed in both deep and shallow implanted specimens, while dislocation loops were observed in the shallow implanted sample that was previously irradiated by 400 keV Ne ions. Cluster size was seen to increase for shallow implants in crystals irradiated with a deep implant (size ~8.5 nm) as compared to crystals treated only to a shallow implant (size ~3.1 nm).

Direct Observation of Growth Behaviour of Athermal Omega-Phase Crystals in a Beta-Titanium Alloy Due to Cooling to 77k Using In-Situ Dark Field Imaging Technique

1999 ◽  
Vol 5 (S2) ◽  
pp. 700-701
Author(s):  
Hajime Matsumoto ◽  
Eiichi Sukedai ◽  
Hatsujiro Hashimoto
Keyword(s):  
Electrical Resistivity ◽  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Electron Diffraction Pattern ◽  
Negative Temperature ◽  
Dark Field ◽  
Beta Titanium Alloy ◽  
Dark Field Imaging ◽  
Ω Phase ◽  
Beta Titanium

INTRODUCTIONIt has been reported by many authors that metastable β-Ti alloys such as Ti-Nb, Ti-V and Ti- Mo indicate the negative temperature dependence of electrical resistivity at low temperature since Ames et al., found the dependence on Ti-Nb alloys in 1954. Williams et al., suggested that the phenomenon resulted from formation of athermal co-phase crystals. In order to clarify the origin, electron diffraction pattern analyses were carried out using a specimen cooling stage and both of start and finish temperatures of formation of athermal co-phase crystals were decided. However, it is necessary to reveal the morphology of athermal ω-phase crystals to study the relationship between the electrical resistivity change and appearance of athermal ω-phase crystals. On the other hand, although electron diffraction pattern analyses are able to identify the atomic structures of crystals, which appear the diffraction spots, it is not so easy to reveal the detailed morphology of the crystals. Also, it has to consider effects of electron irradiation to transformations.

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