Radiation hardening in Zircaloy-2

Annealed Zircaloy-2 was exposed to fast neutron fluences in the range 0.46 to 6.71 × 10¹⁹ nvt, E > 1 MeV, at temperatures of up to 450°C. The level of radiation hardening, as measured by the change in yield stress after irradiation, increased with irradiation temperature at least up to 380°C.

Post-irradiation annealing treatments showed that radiation anneal hardening occurred after irradiation at temperatures up to 325°C. After irradiation at 375°C, annealing treatments did not produce a further increase in the yield stress above that produced by the irradiation, however the radiation hardening persisted to 450°C. The uniform strain tended to decrease as the amount of radiation anneal hardening increased and as the fast neutron fluence increased above ～5 × 10¹⁸ nvt, E > 1 MeV.

The effects of irradiation temperature and post-irradiation annealing on the yield stress and on uniform strain are explained in terms of the strengthening of radiation damage defect clusters and their increased effectiveness to impede dislocation movement.     

Migration behaviour of vacancies and damage structure recovery in a Fe-based Fe-Cr-Mn-Cu-Mo multi-component alloy

ABSTRACT

A Fe-based multi-component alloy, 60Fe-12Cr-10Mn-15Cu-3Mo, which presents higher yield stress than typical stainless steels (such as 304, 316, and 340), was used to investigate the thermal stability of irradiation-induced defects. Neutron irradiation was carried out at approximately 323 and 643?K using up to 1.3 × 10^?3 and 4.5 × 10^?4 dpa (displacements per atom), respectively. While no defects were accumulated at the high temperature of 643?K, single vacancies were formed after irradiation at the low temperature of 323?K to 1.3 × 10^?3 dpa, and the vacancies became mobile at 423?K. As a result, vacancy clusters were formed. However, as the annealing temperature increased the size of vacancy clusters decreased. Coincidence Doppler broadening measurements indicated that Cu precipitates were the sites of vacancy cluster formation, and the recovery of vacancy clusters became prominent while annealing the irradiated sample at temperatures higher than 423?K. Recovery of vacancy clusters at 573?K, which was not a high temperature, was also observed even in the sample that was irradiated using 2.5?MeV Fe ions at room temperature to 0.6 dpa at damage peak.     

Recrystallization of hexagonal silicon carbide after gold ion irradiation and thermal annealing

Silicon carbide (SiC) single crystals with the 6H polytype structure were irradiated with 4.0-MeV Au ions at room temperature (RT) for increasing fluences ranging from 1?×?10¹² to 2?×?10¹⁵ cm^?2, corresponding to irradiation doses from ~0.03 to 5.3 displacements per atom (dpa). The damage build-up was studied by micro-Raman spectroscopy that shows a progressive amorphization by the decrease and broadening of 6H-SiC lattice phonon peaks and the related growth of bands assigned to Si–Si and C–C homonuclear bonds. A saturation of the lattice damage fraction deduced from Raman spectra is found for ~0.8?dpa (i.e. ion fluence of 3?×?10¹⁴ cm^?2). This process is accompanied by an increase and saturation of the out-of-plane expansion (also for ~0.8?dpa), deduced from the step height at the sample surface, as measured by phase-shift interferometry. Isochronal thermal annealing experiments were then performed on partially amorphous (from 30 to 90%) and fully amorphous samples for temperatures from 200 °C up to 1500 °C under vacuum. Damage recovery and densification take place at the same annealing stage with an onset temperature of ~200 °C. Almost complete 6H polytype regrowth is found for partially amorphous samples (for doses lower than 0.8 dpa) at 1000 °C, whereas a residual damage and swelling remain for larger doses. In the latter case, these unrelaxed internal stresses give rise to an exfoliation process for higher annealing temperatures.     

3D processing map and hot deformation behaviour of a new type Al–Zn–Mg alloy

ABSTRACT

The thermal compression behaviour of Al–Zn–Mg alloy was studied on a thermal simulator machine at the temperature range of 380–540°C and strain rate range of 0.01–10?s^?1. The constitutive equation and 3D processing map of the alloys were established. The microstructure characteristics of the alloy were studied by metallographic observation, electron back-scatter diffraction (EBSD) analysis and transmission electron microscopy (TEM) microstructure analysis. The results show that the peak stress of high-temperature deformation of alloy decreases with the increase of deformation temperature and increases with the increase of strain rate. The dynamic recovery of the alloy occurs at the temperature range of 380–460°C and the strain rate range of 0.01–0.1?s^?1. The dynamic recrystallization of the alloy occurs at the temperature range of 460–500°C and the strain rate range of 0.01–0.1?s^?1. The alloy maintains fine and uniform recrystallized grains at a temperature range of 460–480°C and a strain rate range of 0.01–0.1?s^?1, which is suitable for hot working.     

Beam transport

Abstract

Dopant distribution, electrical activity and damage annealing of high-dose (～5 × 10¹⁵ cm²) Ga-implanted silicon samples annealed by conventional thermal annealing have been studied by alpha particle back-scattering, differential Hall effect and ellipsometry measurements. Back-scattering spectra show that there is no long tail of Ga atoms in the as-implanted samples. Upon annealing these samples the damaged amorphous layer recrystallizes at about 570°C by solid phase epitaxy. During the epitaxial regrowth the dopant atom distribution seems to be modified. Further, very high levels of electrical activaton of Ga-atoms (～3 × 10²⁰ cm^?3), much higher than the maximum solubility limit of Ga in Si (4.5 × 10¹⁹ cm^?3), is achieved by thermal annealing of the sample at ～570°C. This is comparable to the doping achieved by laser annealing of the Ga implanted Si. All the above three measurements show that there is residual damage in the high dose (?10¹⁵cm^?2) implanted samples after the recrystallization at about 570°C. This may be related to strain in the lattice at the high concentrations of metastable substitutional Ga atoms. Annealing at higher temperature reduces the electrical activity of Ga atoms, possibly by driving out the metastably high substitutional concentrations of Ga-atoms into electrically inactive clusters or precipitates.     

Thermal expansion and phase changes of 16Kh12V2FTaR steel in temperature range from 20 to 1000 °C

The article presents the results of investigation of thermal expansion of 16Kh12V2FTaR steel in the temperature range 20–1000 °C. Measurements were carried out by dilatometric method with the error (1.5–2)×10^?7 K^?1. The temperature dependences of thermal coefficient of linear expansion of steel have been obtained in ferrite-martensite and ferrite-perlite states, and reference tables have been calculated. Influence of samples cooling rate on martensite phase formation is shown.     

Thermal expansion of ChS-139 steel in temperature range 20–720 °C

The article presents the results of investigation of thermal expansion of ChS-139 steel in the temperature range 20–720 °C. Measurements were carried out by dilatometric method with DIL-402C unit manufactured by NETZSCH (Germany) with the error (1.5–2)×10^?7 K^?1. The approximation dependences of thermal coefficient of linear expansion on temperature have been obtained and reference tables have been calculated. The abnormal change of expansion coefficient above 550 °C is shown, and the explanation of the phenomenon is given.     

Effect of low dose neutron irradiation on the mechanical properties of an AIMgSi alloy

Abstract

An AlMgSi alloy prepared in two different conditions of age-hardening was neutron irradiated to fast fluences up to 2.5 × 10¹⁸n cm^?2 at 50°C. Postirradiation tensile and hardness tests were performed in the range from room temperature up to 350°C. The results show that the alloy in its soft and hard conditions exhibits a pronounced degree of irradiation-induced softening. The degree of softening is found to be dependent upon the ageing treatment given to the alloy before irradiation. The observed softening is suggested to be brought about by irradiation-induced dissolution of the age-hardening precipitates present before irradiation.     

Thermal conductivity of γ-irradiated lif at low temperatures

The thermal conductivity of LiF single crystals which where γ-irradiated in a Co⁶⁰ -source at room temperature with doses ranging from 8.5 10⁵ Rad to 3.6 10⁸ Rad was measured in the temperature range from 60 mK to 100 K. The most heavily irradiated specimen was also measured after annealing treatments at temperatures between 260°C and 400°C. From a numerical analysis of the thermal conductivity data we derive the following interpretation of the thermal resistivity due to the radiation damage. The defects created are threefold: (a) F-centers which act as point defects, (b) small aggregates of point defects with a diameter of about 10 Å which are roughly thirty times less numerous than the F-centers (c) large scale aggregates containing several thousands of lattice sites which appear at irradiation doses $\text{?10}{}^7$ Rad. Each of these defects acts on the thermal conductivity in a different temperature range and are identified as interstitial clusters through their characteristic behaviour during irradiation and subsequent annealing.     

Temperature dependence of the radiation-induced hardening of EP-823 steel after 7-MeV Ni++-ion irradiation

Ferritic-martensitic steel 16Kh12MVSFBR (EP-823) is irradiated with 7-MeV Ni⁺⁺ ions to fluences in the range of (2.7–6) × 10²⁰ ion/m² at temperatures of 350–600°C. The obtained temperature dependence of steel hardening after irradiation has a non-monotonic character with a maximum at 380°C. This dependence is determined by changes in the steel microstructure with irradiation temperature and correlates with the known experimental data on neutron irradiation and results of mathematical-statistical simulation using the bootstrap procedure and a neural-network model of changes in the strength properties of 12% chromium steels of the ferritic-martensitic class after neutron irradiation.     

Damage evolution and multi-scale analysis of carbon fiber-reinforced cross-ply laminate with thermal residual stress

In order to study the mechanical and thermal properties of carbon fiber-reinforced cross-ply laminate, a macroscopic [90/0]_8S cross-ply laminate model and a unit cell of fiber regular distribution near the [90/0]_8S laminate interlaminar zone with plastic matrix and interface were created. Then the damage initiation discipline details of [90/0]_8S cross-ply laminate are researched, and the effects of interfacial coefficient of thermal expansion on thermal residual stress distribution and damage initiation are researched in detail both based on the macroscopic and microscopic models. It shows that the initial damage of interlaminar interface occurs in macroscopic model and the initial damage in microscopic model occurs both at intralaminar interface and interlaminar cohesive zone. No matter in macroscopic or microscopic model, the residual stress of 6.27 × 10^?6/°C interfacial coefficient of thermal expansion is larger than that of 6.27 × 10^?7/°C interfacial coefficient of thermal expansion. And the initial damage expands more widely in the first one.     

The influence of neutron and proton irradiation on the magnetization of biotite

This paper reports on the results of investigations into the field dependences of the magnetization for biotite in the initial state, after heat treatment at a temperature of 1000°C for 15 min, and after irradiation with 14-MeV neutrons at a dose of 1.2×10¹³ cm^?2 or with 3-MeV protons at a dose of 2.2×10¹⁴ cm^?2. It is demonstrated that the magnetization of biotite drastically increases after neutron and proton irradiation. This effect can be associated with the formation of oxide melt at radiation-induced thermal peaks and the freezing of high-temperature phase states corresponding to magnetite or magnetite-hematite solid solutions.     

Radiation enhanced diffusion in UO2 and (U,Pu)O2

Abstract

The radiation enhanced diffusion (coefficient D*) of U-233 and Pu-238 in UO₂ and (U, Pu)O₂ with 2.5 and 15% Pu was measured during fission in a nuclear reactor. Normal diffusion sandwiches with a thin tracer layer were used. A radio-frequency furnace allowed the temperatures to be varied between 130 and 1400°. Neutron fluxes (7 × 10¹² to 1.2 × 10¹⁴ n cm^?2 s^?1) and irradiation times (56 to 334 h) were also varied to cover ranges of fission rates [Fdot] between 7× 10¹¹ and 6.4 × 10¹³ f cm^?3 s^?1 and of doses F between 4.2 × 10¹⁷ and 3.1 × 10¹⁹ f cm³. Below ～1000°, D* was completely athermal and increased linearly with [Fdot]. It was described by D* = A[Fdot] with A = 1.2× 10^?29cm⁵. A possible temperature dependence was indicated between ～1000and 1200°. The results are explained in terms of thermal and pressure effects of fission spikes and are related with other studies of radiation damage as well as with technologically interesting processes occurring in UO₂ during irradiation.     

Anomalies in the temperature dependences of the bulk and shear strength of aluminum single crystals in the submicrosecond range

The results of measurements of the dynamic yield stress and the ultimate strength of aluminum single crystals in the temperature range from 15 to 650°C, which is only 10°C lower than the melting point, are presented. The measurements are made on samples under the action of plane shock waves with a pressure up to 5 GPa behind the front and of a duration of ～2×10^?7 s. It is found that the dynamic yield stress anomalously increases, attaining, in the vicinity of the melting point, a value four times as high as that measured at room temperature. The dynamic strength of the single crystals in this temperature range decreases approximately by 40%, a high strength being preserved in the state in which melting during extension is expected.     

Hot electron studies of lattice damage created in silicon by implantation of 2.8 MeV protons

Abstract

In this paper we report the results of a study of the annealing properties of the ionized defect density associated with the damage created in the silicon lattice by implantation of 2.8 MeV protons at room temperature. In particular, the annealing of damage created by implanting to a level of 4.43 × 10¹² protons/cm² is reported. The resulting isochronal annealing curve covered the temperature range from 70°C to 460°C. Two major annealing stages are discussed, one a broad stage between 70°C to 200°C and the other an abrupt annealing stage between 440°C to 460°C. Between the temperature range 200°C to 440°C the number of ionized defects remained relatively constant. Above 460°C no detectable effects of the proton implantation remained.     

Swift heavy ion provoked structural, optical and electrical properties in SnO2 thin films

SnO₂ thin films grown on glass substrates at 300 ^°C by reactive thermal evaporation and annealed at 600 ^°C were irradiated by 120 MeV Ag⁹⁺ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at a certain fluence of irradiation. X-ray diffraction (XRD) revealed the crystalline nature of the films. The particle size estimated by Scherrer’s formula for the irradiated films was in the range 10–25 nm. The crystallite size increases with increase in fluence up to 1×10¹² ions?cm^?2, whereas after that the size starts decreasing. Atomic force microscope (AFM) results showed the surface modification of nanostructures for films irradiated with fluences of 1×10¹¹ ions?cm^?2 to 1×10¹³ ions?cm^?2. The UV–visible spectrum showed the band gap of the irradiated films in the range of 3.56 eV–3.95 eV. The resistivity decreases with fluence up to 5×10¹² ions?cm^?2 and starts increasing after that. Rutherford Backscattering (RBS) reveals the composition of the films and sputtering of ions due to irradiation at higher fluence.     

Damage distribution and measure of projected range in proton bombarded GaAs

Abstract

The technique of cross-sectional transmission electron microscopy has been applied to obtain information on the projected range of protons and their damage distribution in gallium arsenide. The crystals were subjected to dosages of 1 × 10¹⁵ to 1 × 10¹⁷ protons cm^?2 and proton energies of 100, 200 and 300 keV. Within this energy range the damage shows a Gaussian distribution about a mean range which correlates closely with LSS values. The experimentally determined damage profiles are found to be essentially independent of proton energy and the temperature of post implantation anneal for a given dosage. The displacement damage as reflected by the damage profiles is found to be linear with proton dose. Finally, it is estimated that defects became visible in unannealed crystals when each atom is, on the average, displaced at least once during irradiation.     

Effect of implantation temperature on the blistering behavior of hydrogen implanted GaN

GaN epitaxial layers were implanted by 100 keV H⁺ ions at different implantation temperatures (LN₂, RT and 300 °C) with a fluence of 2.5×10¹⁷ cm^?2. The implanted samples were characterized using Nomarski optical microscopy, AFM, XRD, and TEM. Topographical investigations of the implanted surface revealed the formation of surface blistering in the as-implanted samples at 300 °C and after annealing at higher temperature for the implantation at LN₂ and RT. The physical dimensions of the surface blisters/craters were dependent on the implantation temperature. XRD showed the dependence of damage-induced stress on the implantation temperature with higher stress for the implantation at 300 °C. TEM investigations revealed the formation of a damage band in all the cases. The damage band was filled with large area microcracks for the implantation at 300 °C, which were responsible for the as-implanted surface blistering.     

Diffusion of Butylated Hydroxy Toluol (BHT) in PVC Films

Abstract

The diffusion coefficient of butylated hydroxy toluol (BHT) in solvent casted PVC films from tetrahydrofurane (THF) was studied by UV spectroscopy. Diffusion coefficient of BHT in PVC at 140, 160 and 180°C were determined as 1.0 × 10^?12 3.0 × 10^?12 and 6.0 × 10^?12 m²/s. The activation energy of diffusion (E_a) was 66 kj/mol.

IR spectroscopic work showed that the complete removal of THF was possible by heating films 15 minutes at 140 °C, but that caused formation of C=0 groups in PVC. No dehydrochlorination of films was observed even for heating them at 180 °C for 60 minutes.

Antioxidant BHT is volatile at high temperatures, so it is not advisable to use it for high temperature applications.     

Positron annihilation in electron-irradiated n-type gap crystals

Abstract

The defects in n-GaP crystals irradiated by 2.3 MeV electrons up to 1 × 10¹⁹ cm^?2 at RT were studied by means of positron annihilation (angular correlation) and electrical property measurements. It was found that positrons are trapped in some radiation-induced vacancy-type defects (acceptors) but that the effect saturates at high electron fluences (D1 × 10¹⁸ cm^?2). The trapping rate in irradiated samples increases with temperature in the range 77–300 K. Post-irradiation isochronal annealing reveals the positron traps clustering at about 200–280°C. All positron sensitive radiation-induced defects disappear upon annealing up to 500°C.