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• 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]

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]

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]

• 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]

• 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]

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]

[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]

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]