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In this work, we studied the evolution of vacancy-like defects and the formation of brittle precipitates in a reduced-activation V−Cr−Mn medium-entropy alloy. The evolution of local electronic circumstances around Cr and Mn enrichments, the vacancy defects, and the CrMn3 precipitates were characterized by using scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and positron annihilation spectroscopy. The microstructure measurements showed that the Mn and Cr enrichments in the as-cast sample significantly evolved with temperature, i.e., from 400 °C, the Cr/Mn-segregated regions gradually dissolved into the matrix and then disappeared, and from 900 °C to 1000 °C, they existed as CrMn3 precipitates. The crystallite size of the phase corresponding to CrMn3 precipitates was about 29.4 nm at 900 °C and 43.7 nm at 1000 °C. The positron annihilation lifetime results demonstrated that the vacancies mediated the migration of Cr and Mn, and Cr and Mn segregation finally led to the formation of CrMn3 precipitates. The coincidence Doppler broadening results showed that the characteristic peak moved to the low-momentum direction, due to an increase in the size of the vacancy defects at the interface and the formation of CrMn3 precipitates. [ABSTRACT FROM AUTHOR]

• Two W heavy alloys (WHAs) are examined for radiation resistance. • The WHAs have different Fe and Ni concentrations. • Low-dose irradiation inflicts negligible surface damage to both WHAs. • High-dose irradiation causes surface damage, but to a lesser extent than on pure W. • The WHAs have significant potential for application in nuclear materials. Tungsten-nickel-iron (W-Ni-Fe) alloys, commonly known as W heavy alloys (WHAs), exhibit enhanced ductility, thermal conductivity, and mechanical attributes. These properties render WHAs highly suitable as plasma-facing materials in lieu of pure W. This investigation examines the irradiation resistance of two WHAs—97W-2Ni-1Fe and 90W-7Ni-3Fe—by subjecting them to He ion irradiation at doses reaching 5 × 1017 ions/cm2. The study establishes that low-dose irradiation (1 × 1017 ions/cm2) inflicted negligible surface damage on both WHA compositions. Nonetheless, increasing the radiation dose to 5 × 1017 ions/cm2 led to observable surface impairments, albeit at a reduced magnitude when compared to pure W. An array of analytical methods was employed to characterize irradiation-induced microstructures and void swelling, including positron annihilation spectroscopy, thermal desorption spectroscopy, and transmission electron microscopy. These analyses revealed that low-dose irradiated WHAs predominantly generated vacancy-type defects. Moreover, these defects evolved into He m V n and He m V n -NiFe complexes as the irradiation dose increased. Concurrently, He bubble density escalated with rising irradiation dosage. When subjected to an irradiation dose of 1 × 1017 ions/cm2, both alloys manifested desorption levels approximately 6.5 times greater than that observed in pure W. The findings of this investigation offer valuable insights to the understanding of WHA irradiation behavior in nuclear materials. [ABSTRACT FROM AUTHOR]

The micro-defects evolution of (Al 0. 33 Cr 0. 21 Fe 0. 28 Zr 0.18)O 2 and (Al 0. 33 Cr 0. 2 Mn 0. 09 Fe 0. 22 Zr 0.16)O 2 thin films irradiated with low energy (60 eV) hydrogen ions (H+) is investigated through Transmission Electron Microscopy (TEM) and the slow positron Doppler broadening spectroscopy (DBS) technique in this work. The results revealed that some perfect dislocation loops with Burgers vector b = a/2<1 1 0> were observed as the quaternary (Al 0. 33 Cr 0. 21 Fe 0. 28 Zr 0.18)O 2 irradiated with a fluence of 5.2 × 1022 cm−2. The micro defects are mainly vacancy (V), hydrogen vacancy complex (i.e. H–V complex), and vacancy dislocation loops. However, after the fluence increased to 1.2 × 1023 cm−2, the phase of (Al 0. 33 Cr 0. 21 Fe 0. 28 Zr 0.18)O 2 transformed from FCC structure to amorphous, suggesting that the weak ionic bonds between the cations with O. The defects mainly exist as large amounts of hydrogen bubbles, some H–V complex and few voids. As the addition of little Mn element, the phase of quinary (Al 0. 33 Cr 0. 2 Mn 0. 09 Fe 0. 22 Zr 0.16)O 2 was unstable and easily produce precipitate under the irradiation temperature. And the micro-defects in (Al 0. 33 Cr 0. 2 Mn 0. 09 Fe 0. 22 Zr 0.16)O 2 irradiated with 5.2 × 1022 cm−2 mainly exist as V, H–V complex and some vacancy clusters. While the fluence increase to 1.2 × 1023 cm−2, the defects mainly exist as H–V complex and hydrogen bubbles. [Display omitted] • The defects evolution of the two HEOs induced by H+ irradiation behave differently. • The ionic bonds between the cations with O in (Al 0. 33 Cr 0.. 21 Fe 0. 28 Zr 0.18)O 2 are weak. • As the addition of Mn, the phase of (Al 0. 33 Cr 0. 2 Mn 0. 09 Fe 0. 22 Zr 0.16)O 2 was unstable. • Hydrogen diffuse into both the surface and inner direction of films. [ABSTRACT FROM AUTHOR]

The formation of mono-vacancy, vacancy clusters and hydrogen-vacancy complexes with 30 keV H ion-irradiated pure titanium at different doses and temperatures was measured using by Positron annihilation spectroscopy (PAS). Results show a large number of H m V n clusters and vacancy-like defects in the samples irradiated at for room temperature, and that the formation of H m V n (m > n) at the sample irradiated at a high dose inhibits the increase of the S parameter. At increased irradiation temperature, the shrinkage of vacancy clusters and the effective open volume of defects decrease the S parameters. The high-temperature irradiation results in decreased vacancy-type defect concentration, and some hydrogen atoms diffuse from the cascade region to the track region, forming a large number of hydrogen-vacancy complexes in the track region. The coincidence Doppler broadening spectroscopy, an element analysis method, used to detect hydrogen in the ion-irradiated pure titanium sample, and results show hydrogen-related peaks in the high-momentum region, which may be due to the information of positron annihilation in the covalent bond formed by the H and the Ti elements. The increased radiation dose and temperature contribute to the formation of the hydrogen vacancy-complex, and the positron annihilation in high-momentum regions easily obtain hydrogen-related information. • The increased radiation dose and temperature contribute to the formation of the hydrogen vacancy-complex (H m V n). • The formation of H m V n (m > n) at the sample irradiated at a high dose inhibits the increase of the S parameter. • Hydrogen-vacancy complexes (H m V n) formed as hydrogen atoms deposited in the material. [ABSTRACT FROM AUTHOR]

Here, the storage sites of hydrogen in FeCr alloy, namely (H, He)–V nano-clusters with open volume, have been investigated by first-principles calculations and positron annihilation spectroscopy. The positron lifetimes in the nano-clusters obtained by theoretical calculations and experiments were compared. These results suggest that positron is sensitive to the relative position of the gas atoms decorating the open volume; and a helium atom forms a more repulsive ion core than a hydrogen atom when it occupies the vacancy, resulting in a decrease in positron lifetime. Interpretation of the PAS data was successfully combined with theoretical calculations, and allowed us to determine the defect status in specimens after H/He irradiation with different implantation patterns. The speculated kinds of hydrogen storage sites formed after irradiation are summarized. For the He-ions pre-implanted situation, the helium-vacancy clusters or bubbles forming in advance may recombine with H atoms to form stable He–H–V complex. • Positron is sensitive to the relative position of the H atoms decorating the open volume. • Various point defect structures were modeled. • The lifetime values of positrons in various (H, He)-V complexes are given. • The kinds of defects formed after He/H sequential-ion irradiations are summarized. [ABSTRACT FROM AUTHOR]

Abstract This study aims to investigate the effects of temperature and dose on the vacancy-defect evolution in 304L stainless steel irradiated by the triple beam of Ni, H, and He ions below 673 K, which is relevant to water-cooled nuclear energy facilities. The irradiation experiments were performed simultaneously using 150-MeV Ni ions whose energy was degraded by passing through a tantalum foil of 8.5-μm thick, 100-keV H ions, and 200-keV He ions at 473, 523, 573, 623, and 673 K, respectively. The irradiation-induced microstructures in the steel were probed by the slow positron beam technique. The results show that the S parameter of the irradiated sample decreases as the temperature increases, and the S parameter of the high-dose irradiated sample decreases further. We explained the results by analyzing the structure of the defects in the irradiated samples at various temperatures and the effects of the annealing effect. In addition, the analysis of the S W plots reveals the transition of the helium-vacancy cluster to the overpressured He m V n (m > n) cluster under the influence of temperature and irradiation dose. [ABSTRACT FROM AUTHOR]

Abstract The aim of investigating the annealing effect induced by helium/hydrogen ion irradiation on the micro-defects of ferritic/martensitic (FM) steel is to gain a basic understanding on the development of fusion reactor components. In this study, 250 keV He2+ and 130 keV H+ were used for irradiation. Then, micro-defects were annealed isochronally between 423 K and 673 K, and were monitored by the slow positron beam Doppler broadening technique. The results revealed that the He ions implanted into the steels combined with vacancies to form He n V m clusters, and were likely to grow and form overpressured He n V m clusters by thermal activation. The S-W line of the irradiated specimen deviated the line segment, which indicates the formation of overpressured He n V m clusters in the He-irradiated steel. Moreover, the ΔS-E curves indicate residual vacancies that were induced by He-irradiation at 723 K and later migrated toward the bulk of the sample at 423 K. Subsequently, the vacancies tended to migrate to the sample surface as the annealing temperature increased. The S parameter of the He+H-irradiated sample was much larger than that of all other samples, owing to the synergy effect of H and He. After annealing at 423 K, the H-V clusters decomposed and the hydrogen atoms in the He+H-irradiated sample escaped from the surface leaving a large number of vacancies. [ABSTRACT FROM AUTHOR]

The formation of helium bubble precursors, i.e., helium-vacancy complexes, was investigated for Fe9Cr alloy, which was uniformly irradiated by using 100 keV helium ions with fluences up to 5 × 10 16 ions/cm 2 at RT, 523, 623, 723, and 873 K. Helium-irradiation-induced microstructures in the alloy were probed by positron annihilation technique. The results show that the ratio of helium atom to vacancy (m/n) in the irradiation induced He m V n clusters is affected by the irradiation temperature. Irradiated at room temperature, there is a coexistence of large amounts of He m V 1 and mono-vacancies in the sample. However, the overpressured He m V n (m > n) clusters or helium bubbles are easily formed by the helium-filled vacancy clusters (He m V 1 and He m V n (m ≈ n)) absorbing helium atoms when irradiated at 523 K and 823 K. The results also show that void swelling of the alloy is the largest under 723 K irradiation. [ABSTRACT FROM AUTHOR]

Transmutation helium may causes serious embrittlement which is considered to be due to helium from clustering as a bubble in materials. Suppression of transmutation helium can be achieved by introducing trapping sites such as dislocations and impurities in materials. Here, effects of intentionally-induced dislocations and hydrogen on helium migrate and release behaviors were investigated using thermal desorption spectrometry (TDS) technique applied to well-annealed and cold-worked Fe9Cr alloys irradiated by energetic helium/hydrogen ions. Synchronous desorption of helium and hydrogen was observed, and the microstructure states during helium release at different temperatures were analyzed. High thermally stable He n D type complexes formed in cold-worked specimens, resulting in the retardation of helium migration and release. The existence of hydrogen will strongly affect the thermal helium desorption which could be reflected in the TDS spectrum. It was confirmed that hydrogen retained in the specimens can result in obvious delay of helium desorption. [ABSTRACT FROM AUTHOR]

In this work, we studied the resistance to helium-irradiation-induced swelling of the Fe 6 Cr 1.2 Mn 0.8 Cu 1.5 Mo 0.3 V 0.2 alloy containing highly thermally stable Cu nanoprecipitates for nuclear applications using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The results show that the Cu nanoprecipitate/matrix interface and the nanoprecipitate itself can trap helium bubbles, creating open volume sinks of helium bubbles; large helium bubbles tend to be dispersed at the interface, while small helium bubbles are distributed in the matrix. The SAXS results indicate that the average size of helium bubbles is 1.3–1.7 nm, and the distribution of helium bubbles in the two samples varies due to the difference in Cu nanoprecipitation/matrix interface density, which was also verified via TEM. In addition, a low swelling ratio (0.05%/dpa) of the alloy was calculated, further confirming the feasibility of heterogeneous nanoprecipitation management of helium damage in irradiation tolerant materials. These nanostructured materials have the potential to reduce the helium effect by providing more nucleation sites for helium bubbles. • The stability of Cu nanoprecipitates will provide additional proof for the effectiveness of the Cu nanoprecipitates in managing the He bubble. • Cu nanoprecipitates form an interface with a typical misfit (22.6 %) with the matrix providing a place for helium atoms entering the material. • The nanoprecipitates themselves can manage the helium atoms by trapping the helium bubbles inside them. • The swelling rate of the Fe 6 Cr 1.2 Mn 0.8 Cu 1.5 Mo 0.3 V 0.2 alloy (∼0.05%/dpa) is lower than that of FeCrWTi–Y 2 O 3 ,ferrite ODS and other alloy. [ABSTRACT FROM AUTHOR]

Fe-Cu systems, model alloys of nuclear reactor pressure vessel (RPV) steels, heat treatments by annealing and quenching, are studied by the positron annihilation technique and high-resolution SEM. The different effect of annealing and quenching on the formation of Cu precipitates was discussed. The ultrafine Cu precipitates, which are formed in Fe- x wt.% Cu ( x = 1.0 and 1.5) alloys after thermal annealing, are observed clearly and no obvious Cu precipitates were found in the quenched alloys. The annealing temperature has an effect on the concentration of Cu precipitates, which leads to a change of the proportion of positron annihilation in the Cu precipitates, and this can be reflected by the change of the W parameters. Positron annihilation Doppler broadening spectroscopy results show that Cu precipitates formed during annealing at 1173 K still exist when the annealing temperature is higher than 1453 K. SEM measurements were used to observe the size and the distribution of Cu precipitates in the samples, after using different annealing temperature. [ABSTRACT FROM AUTHOR]

An element analysis method, coincidence Doppler broadening spectroscopy of slow positron annihilation, was employed to detect helium in ion-irradiated Fe9Cr alloys. Spectra with higher peak to background ratio were recorded using a two-HPGe detector coincidence measuring system. It means that information in the high-momentum area of the spectra can be used to identify helium in metals. This identification is not entirely dependent on the helium concentration in the specimens, but is related to the structure and microscopic arrangement of atoms surrounding the positron annihilation site. The results of Doppler broadening spectroscopy and transmission electron microscopy show that vacancies and dislocations were formed in ion-irradiated specimens. Thermal helium desorption spectrometry was performed to obtain the types of He traps. [ABSTRACT FROM AUTHOR]

Here, we investigated the irradiation defect in reduced activation ferritic/martensitic steels by slow positron beam. Three ion-irradiation experiments were carried out: (i) He2+irradiation, (ii) H+irradiation and (iii) He2+irradiation followed by H+irradiation, at temperature 450 °C. The presences of vacancy defects, represented by ∆SHe+Hparameter, induced by sequential irradiations was larger than the sum of defects, ∆SHeparameter + ∆SHparameter, caused by single He ions and single H ions. The synergistic effect of He and H was confirmed clearly from the perspective of positron annihilation spectroscopy. [ABSTRACT FROM AUTHOR]

Mechanism of Hydrogen-induced defects and cracking in Ti and Ti–Mo alloy was systematically analyzed from the perspective of microstructure. Results show that more hydrogen atoms can be dissolved in Ti–Mo alloy due to the existence of β phase, and the precipitation amount of hydride is reduced under the same hydrogen charging conditions. The analysis of positron annihilation results show that the solid solution of Mo element reduces the hydrogen induced defect concentration in the alloy and inhibit the combination of hydrogen and defects. At the same time, Mo atom can affect the electronic structure of Titanium hydrides, and then reduce the bonding between titanium atoms and hydrogen atoms, thereby reducing the formation of brittle titanium hydride. The reduction of hydride and hydrogen induced defect concentration significantly decrease the hardening rate of Ti–Mo alloy, thereby effectively reducing the hydrogen embrittlement sensitivity of titanium and inhibiting its hydrogen absorption cracking tendency. • The formation of β phase in Ti–Mo alloy improves the solubility of hydrogen, thereby reducing the precipitation of hydride. • The solid solution of Mo can affect the electronic structure of titanium hydride and weaken the bonding between Ti–H. • The solid solution of Mo can reduce the concentration of hydrogen-induced defects in Ti–Mo alloy. • Reducing the concentration of hydride and hydrogen induced defect can inhibit hydrogen absorption cracking tendency. [ABSTRACT FROM AUTHOR]

The oxidation behavior of body-centered cubic (bcc) structure Cr20Mn17Fe18Ta23W22 refractory high-entropy alloy (RHEA) and the microdefects induced by hydrogen ions before and after oxidation were investigated. The results revealed that compared with oxidizing Cr20Mn17Fe18Ta23W22 at 800 °C (6.7 °C/min) for 4 h (ST3, Ar:O2 = 3:1), the heating procedure of oxidizing Cr20Mn17Fe18Ta23W22 at 300 °C (6 °C/min) for 2 h and then increased to 800 °C (5 °C/min) for 4 h is more conducive to the production of oxides without spalling on the surface, i.e., HT1 (Ar:O2 = 1:1), HT2 (Ar:O2 = 2:1) and HT3 (Ar:O2 = 3:1) samples. The oxidation of Cr20Mn17Fe18Ta23W22 RHEA is mainly controlled by the diffusion of cations instead of affinities with O. Additionally, HT1 and HT3 samples irradiated with a fluence of 3.9 × 1022 cm−2 hydrogen ions (60 eV) were found to have a better hydrogen irradiation resistance than Cr20Mn17Fe18Ta23W22 RHEA. The microdefects in irradiated Cr20Mn17Fe18Ta23W22 mainly existed as hydrogen bubbles, hydrogen-vacancy (H-V) complexes and vacancy/vacancy clusters. The microdefects in irradiated HT3 were mainly vacancies and H-V complexes, while the microdefects in irradiated HT1 mainly existed as vacancies and vacancy clusters, as large amounts of hydrogen were consumed to react with oxides on the HT1 surface. The oxides on the surface of the HT3 sample were more stable than those on HT1 under hydrogen irradiation. [ABSTRACT FROM AUTHOR]

• High concentration of hydrogen induces martensitic transformation. • Defects induced by hydrogen-charged may be dislocations. • Hydrogen desorption peaks shift to higher temperature for annealing specimen. • Positron annihilation technique studies the evolution of hydrogen and defects. The effects of dislocations and hydrogen concentration on the hydrogen embrittlement (HE) in 316 austenitic stainless steels (316SS) were systematically investigated in the present study. The results revealed a decrease in tensile strength and ductility of 316SS after hydrogen charging. Furthermore, the severity of HE was dependent on the hydrogen concentration. The results of x-ray diffraction revealed the presence of martensite in the hydrogen-charged (50 mA /cm2) specimen annealed at 1000 ℃. This was attributed to the internal stress originating from hydrogen-induced lattice expansion. The analysis of the fracture surface of all the specimens revealed an increase in the brittleness with the absorption of hydrogen. An increase in the hydrogen concentration induced a transformation of the fracture mode i.e., from ductile dimple fracture to cleavage and intergranular fractures. The evolution of hydrogen in 316SS was associated with the defects induced by deformation. The shift in the major desorption peaks of the annealed specimen to the high-temperature region indicated the formation of effective hydrogen-trapping sites during hydrogen-charging. The specimens were subjected to positron lifetime spectroscopy and thermal desorption spectroscopy. The results for the raw specimen, charged at 20 mA /cm2, revealed the gradual escape of hydrogen atoms and recovery of vacancy defects with an increase in the annealing temperature. In addition, the hydrogen-induced and cold rolling-induced dislocations was preserved. [ABSTRACT FROM AUTHOR]

To investigate the influence of different rhenium contents on the helium desorption behavior in tungsten–rhenium alloys, pure tungsten and tungsten–rhenium alloys were irradiated with helium under the same conditions. All irradiated samples were characterized using TDS and DBS techniques. The results indicate that the addition of rhenium can reduce the total helium desorption quantity in tungsten–rhenium alloys and slightly accelerate the reduction in the concentration of vacancy-type defects accompanying helium dissociation. The desorption activation energy of helium is approximately 2 eV at the low-temperature peak (~785 K) and about 4 eV at the high-temperature peak (~1475 K). An increase in rhenium content causes the desorption peak to shift towards higher temperatures (>1473 K), which is attributed to the formation of the stable complex structures between rhenium and vacancies. Besides, the migration of He-vacancy complexes towards traps and dynamic annealing processes both lead to the recovery of vacancy-type defects, resulting in a decrease in the positron annihilation S parameters. [ABSTRACT FROM AUTHOR]

• Helium diffusion and desorption behavior was researched by DBS and TDS measurements. • Helium atoms combining with dislocation change the distribution of electron density. • Helium atoms trapped by dislocations form relatively stable complexes. • Dislocations inhibit the helium radiation damage. Suppression of transmutation helium can be achieved by introducing trapping sites such as dislocation and grain boundary in nuclear materials. In order to understand role of dislocations in helium irradiation effect in metal, positron annihilation spectroscopy and thermal desorption measurements were performed to study the interaction of helium atoms with dislocation in deformed Fe-9 wt.Cr alloys irradiated by 10 keV helium ions. The formation of irradiation defects and the thermal stability of helium-defect complexes are discussed. Analyzing the parameters of positron spectrum, the introduced dislocations will change the positron parameters of irradiated samples, which demonstrate that the dislocation has changed normal irradiation effects. Judging from thermal desorption spectrum, we can see the helium desorption peak of the deformed sample is ahead of well-annealed sample. [ABSTRACT FROM AUTHOR]

Hydrogen behavior and its related property degradation have been long-standing problems for structural materials used in hydrogen energy. The hydrogen atoms can easily interact with vacancy defects, forming hydrogen vacancy complexes which play an important role in the hydrogen-induced structural damage. However, the interaction mechanisms and its evolutions are still unclear. In this work, the hydrogen behavior and the interaction between hydrogen with defects in pure titanium implanted by 30 keV and 50 keV hydrogen ions were studied by positron annihilation spectroscopy. The implantation doses were 5 × 1016 H/cm2, 1 × 1017 H/cm2 and 5 × 1017 H/cm2, respectively. The results show that the structural damage of pure titanium is positively correlated with the ion implantation energy. For the implantation of 50 keV hydrogen ions, a large number of hydrogen atoms are deposited in the samples. With the increase of implantation dose, the formation of hydrogen vacancy complexes (H m V n) reduces the effective open-volume of defects and changes the structural features of defects in implanted samples, thus suppressing the formation of vacancy defects and causing the damage range shifting from the peak damage (PD) region to the near surface (NS) region. Eventually, the movement of hydrogen atoms intensifies, and the "hydrogen peak" becomes more obvious. The chemical information related to deposited hydrogen atoms can be easily identified in the processing and analysis of positron annihilation results. • The formation rate of vacancy type defects increases in direct proportion to the implantation energy. • Implantation dose promoted the formation of hydrogen vacancy complex. • The increase of the proportion of hydrogen vacancy complex leads to the inhibition of vacancy formation. • With the increase of hydrogen concentration, the "hydrogen peak" signal is more obvious. [ABSTRACT FROM AUTHOR]

Zhu, T. and Zhang, F., 2020. Design of marine two-way voice communication system based on human-computer interaction. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1389-1394. Coconut Creek (Florida), ISSN 0749-0208. In order to improve the long-distance transmission and speech receiving and receiving ability of marine bidirectional voice communication, the marine bi-directional voice communication transmission technology based on human-computer interaction is proposed in this paper. The channel equalization model of marine bi-directional speech communication is designed to modulate the marine bi-directional speech communication signal in the space-disguised coherent multi-path channel of marine bi-directional speech information transmission, and the linear equalization controller is used to filter the interference. The fractionally spaced equalizer is designed to deal with the anti-interference of the marine bidirectional speech communication signal, to improve the real-time performance of the marine bi-directional speech transmission, and to design the receiver at the output terminal to realize the accurate feedback of the marine bi-directional speech communication signal. The hardware modularization design of marine bi-directional speech communication system based on man-machine interaction model is carried out. The main function modules of the system include data receiving module, speech information processing module, human-computer interaction module and receiver conversion module. The simulation results show that the proposed method has low bit error rate (BER) for long-distance transmission of marine bi-directional speech communication signals, and can realize real-time monitoring and voice communication of marine bi-directional speech communication. [ABSTRACT FROM AUTHOR]

The evolution of defects with isochronal annealing between 373 and 1273 K in 316L stainless steels, irradiated by helium ions at room temperature (RT), has been studied by the slow positron Doppler broadening spectroscopy (DBS). The results showed that with annealing temperature between RT and 673 K, the S parameters of sample were maintained. It indicates that below 673 K, on the one hand, some vacancies introduced by irradiation were gathered to form vacancy clusters and on the other hand, some vacancies migrated and recovered. From 773 K to 1073 K, there was continuous growth of He n V m cluster, resulting in rapid increasing of S parameter. After 1073 K, unstable He n V m clusters dissociated into vacancies and He atoms. The vacancies were vanished rapidly, which decreases the concentration of vacancy defects, leading to decline of S parameter. [ABSTRACT FROM AUTHOR]

The Fe1.0Cu alloy was irradiated by 2 MeV Fe ions to a peak dose of 0.06dpa, 0.45dpa and 1.35dpa, respectively. The irradiation evolution of Cu precipitates in Fe1.0Cu alloy was studied at various depths by positron annihilation spectroscopy. The values of the S parameters directly indicate the formation of vacancy clusters. The S-W relationship showed that Cu n V m complexes (n > m) dominated the microstructure in the track region. Vacancy clusters and Cu n V m complexes (n < m) were the main defect types in the damage region. There finding were supported by the results of the performed theoretical calculations. The coincidence Doppler broadening showed that the Cu precipitates formed easily at a low irradiation dose, and that the irradiation-induced Cu precipitation was enhanced by the increase of the irradiation dose in the track region. We showed that the Cu precipitates finally reach a steady-state morphology under multiple active processes. [ABSTRACT FROM AUTHOR]

To investigate the thermal evolution of vacancy-type defects and the relationship between the evolution of vacancy-type defects and the formation of fuzz structure on the surface of W-Ni-Fe heavy alloys irradiated with He ions, isochronal annealing treatments at temperatures from 100 °C to 1000 °C were conducted on the irradiated 97W-2Ni-Fe alloy. The evolution of microdefects was characterized by positron annihilation spectroscopy (PAS). Thermal desorption spectroscopy (TDS), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to supplement the positron annihilation method. A large number of vacancy-type defects were produced in the 97W-2Ni-Fe alloy after irradiation at room temperature and isochronal annealing, and the main defect types of positron capture changed at three stages: RT-600 °C, 600–800 °C, and 800–1000 °C. SEM found that a large number of nanoscale protrusions appeared on the surface of samples annealed at 800 °C, and these nanoscale protrusions were seeds of fuzz structures. The formation of fuzz structure is closely related to the movement of vacancy-type defects by PAS, TDS, SEM, and other characterization methods. In addition, we found that the high density Ni and Fe in the matrix phase of the 97W-2Ni-Fe alloy as He capture points would accelerate the nucleation and growth of He bubbles and promote the growth of the fuzz structure. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement (HE) can lead to the unintentional fracture of large engineering materials, resulting in severe economic losses and safety hazards. It is critical to explore economical and scalable solutions to overcome the challenges of HE. In this work, the HE resistances of four face-centered cubic (FCC) concentrated solid solution alloys (CSAs), including NiFe 20 , NiCoCr, NiCoCrFe, NiCoCrFeMn, and pure Ni were comprehensively investigated and compared by using TDS, EBSD and TEM. It was found that Fe and Cr element can effectively inhibit the solubility of deuterium in the CSAs and alleviate the HE behaviors. In contrast, Mn element significantly increases the solubility of deuterium and caused brittle fractures. Tensile experiments were performed to compare the HE sensitivity of CSAs. The tensile strength of pure Ni and NiFe 20 alloys decreased after deuterium charged, whereas the tensile strength of NiCoCr, NiCoCrFe and NiCoCrFeMn alloys increased. Based on the experimental results, it is deduced that deuterium atoms promote dislocation accumulation and twin growth by reducing the stacking fault energy, which eventually leads to an increase in yield strength and a decrease in plasticity. In addition, the accumulation of deuterium atoms near grain boundaries and cracks during deformation leads to dislocation pinning and stress concentration, which ultimately promotes crack nucleation and propagation. The HE resistances of CSAs are strongly influenced by the deuterium concentration, which depends on the effects of constituent elements and deuterium charging time on the deuterium concentration. Collectively, the specific alloying elements play more important role for the HE resistances of CSAs than the number of elements in the current study. These results provide valuable insights for further understanding and design higher HE resistance CSAs in the future. [Display omitted] ● The addition of Fe and Cr elements to CSAs effectively inhibits deuterium dissolution and enhances the resistance to HE. ● The addition of the Mn element to CSAs significantly promoted deuterium dissolution and caused HE fractures. ● Deuterium atoms reduce the SFE and promote dislocation propagation and twin growth. ● The accumulation of localized stresses induced by deuterium promote the initiation and propagation of cracks. ● Higher deuterium concentrations and deuterium charging times are more likely to trigger HE. [ABSTRACT FROM AUTHOR]

[Display omitted] • High density dislocations inhibit hydrogen atoms diffusion. • Different types of hydrides were identified by CDB spectrum and theoretical calculations. • Hydrogen concentration decreases with increasing dislocation density. This work aims to elucidate the interaction between hydrogen atoms and pre-introduced dislocations in commercially pure titanium (CP-Ti). Positron annihilation spectroscopy supplemented by the first-principle calculations was utilized to reveal the effects of dislocation densities on the formation of hydride types and the concentration of hydrogen-induced defects in CP-Ti. Results show that, in the hydrogen-charged sample with 40 % deformation, hydrogen-induced damage gradually decreases when the hydrogen enters the sample at a depth of about 350 nm. This finding suggests that the high-density dislocations present in deformed specimens effectively trap hydrogen atoms and inhibit their diffusion, which ultimately mitigate damage within the samples. γ-TiH and δ-TiH 2 hydrides are observed in the hydrogen-charged sample. The thermal desorption spectroscopy results show that the desorption amount of deuterium decreases from 1.14 × 1018 D/cm2 to 5.10 × 1017 D/cm2 with an increase in dislocation density because dislocations inhibit the diffusion of deuterium. In samples with higher deformation, the high dislocation density inhibits the formation of δ-TiH 2 hydrides and promotes the formation of γ-TiH hydrides, which significantly reduce the hardening of samples. These results provide insight into the interaction of hydrogen with pre-introduced defects and provide strong theoretical support for the development and improvement of more damage-resistant materials. [ABSTRACT FROM AUTHOR]

• Two types of titanium hydrides form after electrochemical hydrogen charging. • The formation of hydride leads to lattice expansion. • Hydrogen content affects the concentration and type of hydrogen induced defects. • The titanium hydride and hydrogen-vacancy complex were identified by CDB spectrum. The influence of hydrogen on defect structure in pure titanium was systemically investigated using X-ray diffraction (XRD) and positron annihilation spectroscopy (PAS). The results showed that hydrogen damage was related to hydrogen concentration, and PAS provided a new idea for the study in the formation of hydride and open volume defects. XRD results showed that two types of titanium hydrides were observed in hydrogen-charged samples, i.e., δ-TiH x and ε-TiH 2 , and the degree of lattice expansion and the content of hydride increased with hydrogen content. The variation of the S parameter and W parameter indicated that a great deal of vacancy-type defects formed during electrochemical hydrogen charging, and hydrogen atoms could combine with vacancy to form a certain amount of hydrogen-vacancy complexes (H n V m), meanwhile, the hydrogen damage varied significantly with depth. The effective open volume of vacancy-type defect increased with hydrogen charging concentration, and hydrogen-vacancy cluster transformed into H n V m (n < m) cluster, vacancy defects were gradually dominated. In addition, According to the different annihilation environment of positron in titanium hydrides and hydrogen-vacancy complexes, the existence of titanium hydrides and the existing form of hydrogen in defect could be identified in Doppler broadening spectroscopy (CDB). This provided a new way to identify the formation of hydrides and to detect the existing form of low concentration hydrogen in samples. [ABSTRACT FROM AUTHOR]

The atomic-scale defects such as (deuterium, helium)-vacancy clusters in nuclear energy materials are one of the causes for the deterioration of the macroscopic properties of materials. Unfortunately, they cannot be observed by transmission electron microscopy (TEM) before they grow to the nanometer scale. Positron annihilation spectroscopy (PAS) has been proven to be sensitive to open-volume defects, and could characterize the evolution of the size and concentration of the vacancy-like nanoclusters. We have investigated the effects of He-D interaction on the formation of nanoscale cavities in Fe9Cr alloys by PAS and TEM. The results show that small-sized bubbles are formed in the specimen irradiated with 5 × 1016 He+/cm2, and the subsequent implanted D-ions contribute to the growth of these helium bubbles. The most likely reason is that helium bubbles previously formed in the sample captured deuterium injected later, causing bubbles to grow. In the lower dose He-irradiated samples, a large number of small dislocations and vacancies are generated and form helium-vacancy clusters with the helium atoms. [ABSTRACT FROM AUTHOR]

1 Irradiation defects in w and W-5wt% Re alloys were characterized by DBS,TEM and SEM. 2 Re restricted the behavior of vacancy-type defects in tungsten. 3 The surface irradiation damage such as crystal gap enlargement, grain shedding and pores were observed at different irradiation temperatures. 4 The formation mechanism of the coral-like structure and the Hilly-Gully structure was analyzed. W and W-5wt% Re alloy were irradiated by 50 keV helium ions at RT, 200 °C, 350 °C and 500 °C to investigate the influence of temperature on the microdefects and surface morphology in the sample. The microdefects in the subsurface region and the surface damage caused by irradiation were characterized by Doppler broadening spectroscopy (DBS) of slow positron beam, transmission electron microscope (TEM) and scanning electron microscopy (SEM), respectively. The results show that a large number of vacancy-type defects were produced after helium ions irradiation, especially at 500 °C, the vacancy-type defects of W alloy are higher than that of W-5wt% Re alloy, which indicated that Re restricted the behavior of vacancy-type defects in tungsten to some extent. The surface irradiation damage such as crystal gap enlargement, grain fell off and pores were observed at different irradiation temperatures. Compared with the coral-like structure observed in W, the circular objects and Hilly-gully structure were observed in W-5wt% Re alloy, and both of them increased and grew with the increase of irradiation temperature. It was speculated that the presence of Re led to the difference by analyzing the formation mechanism of the coral-like structure and the Hilly-gully structure. [ABSTRACT FROM AUTHOR]

The nucleation and growth of the helium bubble in the structure material usually were subjected to temperature in a thermodynamic environment. In this study, Y-bearing oxide dispersed strengthened (ODS) ferritic/martensitic steels were used as the research material. The Y-bearing ODS steel samples with a thickness of 30 microns were irradiated successively by helium ions with three energies of 300 keV, 400 keV and 550 keV at room temperature and 450°C respectively. Firstly, the evolution of defects caused by H e + irradiation is analyzed by using slow positron beam Doppler broadening spectroscopy (DBS) in positron annihilation spectroscopy technology (PAS). The formation and growth of helium bubbles are deduced from the changes in the concentration of vacancy-type defects. The increase in the size of the helium bubbles at high temperatures leads to a certain distortion of the crystal lattice, which is also verified by analyzing the grazing incidence X-ray diffraction (GIXRD) patterns. The characterization of radius and concentration of helium bubbles in samples irradiated at room temperature and 450°C have been studied by Small Angle X-ray Scattering (SAXS) and Transmission Electron Microscopy (TEM). The results showed that the intensity (I) ~ q-vector (q) curves of samples vary with irradiation temperature over ranges of 0.13 ≤ q ≤ 4.6 nm−1, which is attributed to the growth of helium bubbles at different irradiation temperature. It is found that the average size of helium bubbles under room temperature irradiation is about 1.78 nm, and the size distribution is narrow, while at the irradiation temperature of 450°C, the size of helium bubbles increases to 2.9 nm, and the size distribution is wider. This result is also verified from the TEM analysis. Besides, the shape of helium bubbles was assumed roughly and tends to spherical with higher temperatures. [ABSTRACT FROM AUTHOR]

The spatial relationship between helium bubbles and dislocation loops was observed in detail by TEM in RAFM steel irradiated with 100 keV helium ion to a fluence of 1 × 1021 He+ • m−2 at 723 K. Two families of dislocation loops were observed, with b = ± <010> and b = ± <100>, and habit planes of (010) and (100), respectively. The striking observation is that all of the loops were decorated with helium bubbles. Meanwhile, bubbles are determined to be located inside the loop plane through the investigation using different g -vectors under zone axes of [111], [001] and [011]. [ABSTRACT FROM AUTHOR]

The evolution of defects and irradiation damage in Ti and Ti-Mo alloy under hydrogen ion irradiation were investigated by slow positron-beam doppler broadening spectroscopy (DBS) and coincidence doppler broadening spectroscopy (CDB), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD results indicate that the existence of the β phase enhances the solid solubility of hydrogen in Ti-Mo alloy. The metastable γ-TiH hydrides are formed in pure titanium after hydrogen ion irradiation, while no hydride is found in Ti-Mo alloy under the same irradiation conditions. Moreover, DBS and CDB results show that hydrogen vacancy-complexes are formed in Ti and Ti-Mo alloys after hydrogen ion irradiation. Calculated doppler curves trend qualitatively agrees well with the experimental results. The TEM results show lower defect concentration and smaller defect sizes in Ti-Mo alloy with (α + β) than pure titanium. The addition of molybdenum significantly refines the grains and increases the density of the interface, which plays an important role in the management of irradiation-induced defects. • Molybdenum alloying increases the solid solubility of titanium alloy to hydrogen. • Molybdenum alloying can reduce hydrogen-induced defects and irradiation damage. • The hydrogen-vacancy complexes were identified by calculated Doppler spectra. [ABSTRACT FROM AUTHOR]

Positron annihilation technology is a nondestructive detection technique to study the microscopic defects in materials. It is well known that the micro defects will redistribute the charge in materials. In this paper, the charge density of helium in iron was calculated by the Vienna Ab initio Simulation Package (VASP) and the positron annihilation parameters were obtained by Doppler program. The results demonstrated that different types of defects in materials will cause a great variety in charge density, which lead to the change of positron annihilation parameters. In a vacancy cluster containing 6 monovacancies, the positron annihilation lifetime decreases rapidly once the number of helium is greater than the number of vacancies. [ABSTRACT FROM AUTHOR]

Owing to its excellent properties, high-entropy alloys (HEAs) have been regarded as a kind of promising candidate structural material for nuclear devices. For the safety concern, it is vital to figure out the compatibility of hydrogen isotopes with the HEAs. In this work, the hydrogen isotope permeation and retention behavior of a representative HEA, CoCrFeMnNi, has been mainly checked by a gas-driven permeation device and a thermal desorption spectra device. The hydrogen isotope permeation parameters have been obtained, which are quite similar to those of the 316L austenitic steels. The hydrogen isotope retention behavior has been compared with that for a reduced activation ferritic/martensitic steel, and the relatively high hydrogen isotope inventory in HEA has been explained by crystalline structure and high density of hydrogen trapping site. [ABSTRACT FROM AUTHOR]

Vanadium alloys are attractive candidate structural materials in future fusion reactors. To evaluate the effects of irradiation on the deuterium retention behavior in vanadium alloys, samples made of V-5Cr-5Ti were irradiated by 5.5 MeV carbon ions. Doppler broadening measurements of the positron annihilation radiation tests were carried out to investigate the defect properties in the irradiated samples. Then the irradiated and virgin samples were implanted with deuterium in an ECR (electron-cyclotron resonance) linear plasma device followed by thermal desorption spectroscopy experiments. It was found that the irradiation process introduced large density of vacancy-type defects and subsequently increased the deuterium retention in the V-5Cr-5Ti, which remains as a serious concern for the vanadium alloys in the application as the structural materials of the fusion blanket. [ABSTRACT FROM AUTHOR]

We have studied the effect of isothermal annealing on the evolution of the open-volume defect and the Cu precipitate in deformed Fe0.15Cu, Fe0.3Cu and Fe0.6Cu alloys. Using the coincidence Doppler broadening, positron annihilation lifetime and the S-W couples, the evolution of local electronic circumstance around the annihilation sites, open-volume defects and interaction between open-volume defects and Cu precipitates were measured as a function of the isothermal annealing temperatures. Cold rolling deformation induced an obvious increment in S parameters due to the formation of open-volume defects. Annealing not only resulted in gradual recovery of open-volume defects and Cu thermal precipitation, but also promoted the combination and interaction between defects and Cu precipitates. The interaction between open-volume defects and Cu precipitates was revealed clearly by the view point of S-W relationship. The S-W interaction for the different Cu m V n complexes was also calculated theoretically by MIKA-Doppler, which supports our experimental observations qualitatively. The results indicate that open-volume defects were formed first after cold rolling, followed by the Cu precipitation and recovery of open-volume defects, Cu precipitates recovered at the end. It is interesting that the trajectory of (S, W) points with increasing annealing temperature formed a similar closed “Parallelogram” shape. It is benefit for revealing the behavior of Cu thermal precipitation and their evolution in various Cu-bearing steels under thermal treatment. In addition, we also investigated the Cu content effect on the Cu precipitation in FeCu alloys, and the Cu precipitate phenomenon was enhanced in higher Cu content alloys. [ABSTRACT FROM AUTHOR]

Well-annealed 316L stainless steel was first cold rolled to 10% and 20% reductions in thickness and then irradiated by 50 keV He+to a dose of 1 × 1020He+/m2at room temperature. Thermal desorption spectroscopy was used to investigate the helium desorption behaviour at different helium trapping states. The results showed that high-density dislocations had stronger inhibitory effect for helium desorption at temperatures from 800 to 1200 K. Positron annihilation Doppler broadening spectroscopy measurements were used to investigate the distribution of helium irradiation-induced defects. TheS–Eand ΔS–Eplots clearly demonstrated that the helium irradiation-induced defects were trapped and restricted in motion by dislocations. The interaction between dislocations and helium irradiation-induced defects in deformed 316L stainless steel was investigated. [ABSTRACT FROM PUBLISHER]

The purpose of the study detailed in this paper is to investigate the evolution of microstructural defects in the Fe‐9Cr binary alloy induced by isochronal annealing from 373 to 1223 K. Positron annihilation lifetime spectroscopy (PALS), Doppler broadening spectroscopy (DBS), positron annihilation lifetime calculation, and transmission electron microscope (TEM) are used to analyze and characterize the change of defect concentration, defect type and the micro‐morphology in the Fe‐9Cr alloy as a function of the annealing temperature. The experimental results showed that, a large number of vacancies and dislocations were found to exist in the untreated Fe‐9Cr alloy. The monovacancy (186.2 ps) in the Fe‐9Cr alloy migrated during annealing from room temperature to 573 K. The annealing temperature at 773 K produce aggregation of dislocations and the formation of dislocation networks, as well as their heterogeneous distribution. When the temperature is further increased to 1073 K, most of the vacancies and dislocations are recovered and a bcc‐fcc phase transmition occurred in Fe‐9Cr model alloy. The dislocation density is continuous decreased with the increase of annealing temperature, the recovery is obvious from 773 K annealing to 1073 K annealing in Fe‐9Cr alloy. [ABSTRACT FROM AUTHOR]

Long-term exposure of structural materials to extreme hydrogen-enriched environments will lead to hydrogen embrittlement, and thus search and design of new alloys with economic and safety benefits against hydrogen embrittlement have become a top priority for the development of many engineering fields. In this work, the hydrogen embrittlement behavior of a new cobalt-free high-entropy alloy (HEA) Fe 27 Ni 28 Mn 27 Cr 18 was systematically studied and compared with a typical quaternary HEA Fe 25 Co 25 Cr 25 Ni 25. Numerous vacancies are produced in the process of electrochemical deuterium charging and the corresponding concentration is related with the solubility of deuterium atoms. Fe 27 Ni 28 Mn 27 Cr 18 has much higher concentrations of deuterium and vacancies than Fe 25 Co 25 Cr 25 Ni 25 , which is attributed to the Mn induced severe lattice distortion and results in different variations of mechanical properties. The ultimate tensile strength (UTS) of Fe 27 Ni 28 Mn 27 Cr 18 increases from 353.73 MPa to 589.50 MPa after electrochemical hydrogen charging while the elongation still remains at 74.73%, and its deformation mechanism is dominated by dislocation proliferation. In contrast, the UTS of hydrogen charged Fe 25 Co 25 Cr 25 Ni 25 decreases from 552.79 MPa to 501.53 MPa and the corresponding elongation also decreases from 74.65% to 67.24%, and the plastic deformation mechanism is dominated by twinning. This work demonstrates an economic cobalt-free HEA with great resistance to hydrogen embrittlement, which would enhance the applications of HEAs in hydrogen-enriched environments. • The severe lattice distortion in Fe 27 Ni 28 Mn 27 Cr 18 promotes the dissolution of deuterium atoms. • Deuterium charging leads to a decrease in the plasticity of the sample and an increase in the yield strength. • Fe 27 Ni 28 Mn 27 Cr 18 alloy has high plasticity and low hydrogen embrittlement susceptibility. [ABSTRACT FROM AUTHOR]

In order to study the microstructural evolution of the He + irradiated FeCrNi model alloy, 140 keV He + ions were implanted into the specimen with the fluence of 1 × 10 15 ions/cm 2 at room temperature. Positron annihilation spectroscopy was used to characterize the evolution of micro defects during isochronal annealing between 423 and 873 K. The decrease of the S parameter between 573 and 623 K has been associated to the annihilation of vacancy clusters, which were not trapped by helium atom. While the decline of the S parameter between 773 and 823 K in the damage region might be caused by the dissociation of He n V m clusters. The dissociated vacancy clusters were unstable and annihilated rapidly, which decreases the concentration of vacancy defects. [ABSTRACT FROM AUTHOR]

To investigate the influence of transmutation rhenium on the irradiation-induced defects in tungsten, H+ and He+ irradiation of 50 keV with a fixed fluence of 1 × 1016 atoms·cm−2 were conducted on W x Re (x =0, 3, 5 and 25 wt.%) alloys, respectively. Doppler Broadening Spectroscopy and Coincidence Doppler Broadening Spectroscopy both based on slow positron beam were employed in the current work to characterize the depth distribution and the chemical surroundings of the irradiation-induced defects. The results showed that under 723K irradiation, Re addition suppressed the accumulation of vacancy-type defects compared with pure W. This suppression was enhanced by increasing Re content in W. An obvious Re-related peak from (7-28) × 10−3 m 0 c was observed in CDB spectra of well-annealed W-Re alloys. The irradiation effect led to the height deviation of Re-related peak. The decrease of the Re-related peak could be attributed to the formation of irradiation-induced defects in irradiated samples, and the reduction of positron annihilation fraction with core electrons of Re. [ABSTRACT FROM AUTHOR]