[en] TEM observation was performed on titanium tritide films at He:Ti ratios of 0.036–0.356. Most helium atoms remained in the TiT₂ lattice until at a He/Ti ratio of 0.06, almost all helium atoms entered the bubbles. The density of helium bubbles in Ti tritide increased with the increase in helium content, while their size distribution remained almost unchanged until the bubbles in the samples begin to interconnect at a He/Ti ratio of 0.247. Helium bubbles preferred to distribute in Ti {111} planes for all the samples. The morphology of helium bubble distribution changes not only with the density of bubbles but also with the strain in the films. Helium tended to migrate to the grain boundaries, and plenty of cracks were developed along the grain boundaries. The extension of cracks to the film surface is the cause for the large bursts of ³He into the atmosphere. The observed microstructural evolution and its dependence on helium concentration, density of bubble, and stress distribution are discussed in terms of diffusion of interstitial He atoms and their clustering.

[en] Two kinds of films were prepared to study the effect of microstructure on helium migration in Ti tritides. Both films showed different release behaviors and helium bubble distributions. In the film consisting of columnar grains, a two-layered structure was observed. Inclusions with a strip feature were found at the grain boundary, and no helium bubbles were distributed in these inclusions. However, helium preferred to migrate to the boundaries of these inclusions. Bubble linkage as a ribbon-like feature developed parallel to the film surface in the film consisting of columnar grains. More cracks were developed at the grain boundaries of the film consisting of columnar grains, although the helium content in the film consisting of columnar grains was less than that in the film consisting of equiaxed grains. A surface region with a small number of bubbles, or “depleted zone”, was observed near the surface. The cracks extending to the film surface were the pathways of the critical helium released from the film. The helium migration was strongly influenced by the grain microstructure. (paper)

[en] The thermal desorption behavior of ion-implanted helium in erbium and scandium films was investigated by means of thermal helium desorption spectrometry. The peak positions of ion-implanted helium desorption are the same for erbium films with different surface morphologies. The degree of denseness of films, however, will affect the amount of released helium as the implanted helium releases through the path of cavities existing in the loose film before thermal desorption. The difference in peak positions of helium desorption from erbium and scandium films may be related to the depth distribution of helium and the degree of denseness of films. The helium implantation depths measured by enhanced proton backscattering spectrometry are 210 and 308 nm. respectively, for erbium and scandium films with the implantation energy of 60 keV. (authors)

[en] Highlights: • The HEA TiZrHfMoNb and its hydrides exhibit excellent ductility and high temperature resistance. • The TiZrHfMoNb hydride is expected to possess superior mechanical properties in the phase transition region. • Both hydrogen distribution and lattice distortion in TiZrHfMoNb hydrides affect the mechanical strength and ductility. -- Abstract: In recent years, high entropy alloys (HEAs) have demonstrated potential applications in nuclear reactors. As a transmutation byproduct in fission reaction or a fuel for fusion reaction, the hydrogen may affect the mechanical properties of HEAs. In this study, the mechanical properties and thermal stability of HEA TiZrHfMoNb and its hydrides are investigated by first-principles calculations. Our results show that the HEA TiZrHfMoNb exhibits excellent ductility and high temperature resistance. After hydrogenation, the hydrides still maintain high ductility with enhanced melting temperature, suggesting that the HEA TiZrHfMoNb is a potential candidate structural material in fusion reactors. Both of hydrogen distribution and lattice distortion in TiZrHfMoNb hydrides are found to affect the mechanical strength and ductility, which is quite different from that in pure HEAs. The TiZrHfMoNb hydrides within the phase transformation region is expected to exhibit superior mechanical performance as compared to the single-phase regions.

[en] Highlights: • The effects of deformation and annealing on the properties of tungsten alloy were investigated. • The strength and toughness of tungsten alloy can be improved by large rotary swaging ratio. • The doping of zirconia prolonged the recovery and recrystallization process of tungsten alloy. • W-1.5ZrO₂ alloy has the best properties after annealing at 1100–1200 °C for 1 h. -- Abstract: W-1.5ZrO₂ alloy bars with two diameters, named as D9 and D5, were prepared by liquid phase method and rotary swaging method. The effects of swaging and annealing on the microstructure and mechanical properties of tungsten alloys were investigated. Under the same swaging ratio, the compressive strength of D5 tungsten alloy and D9 tungsten alloy is 23.27% and 22.37% higty her than that of pure W, respectively. After multi-pass swaging, the diameter of tungsten alloy decreased from 9 mm to 5 mm, and the hardness and compressive strength increased by 14.6% and 21.93%, respectively. After multi-pass rotary swaging, the diameter of tungsten alloy is reduced from 9 mm to 5 mm, and the hardness and compressive strength are increased by 14.6% and 21.93% respectively. The fracture mode has gradually changed from intergranular fracture to trans-granular fracture. Therefore, the strength of tungsten alloy can be improved by adding zirconia and proper swaging process. With the increase of annealing temperature or time, recrystallization and grain growth will be caused. The addition of ZrO₂ can delay the recrystallization of tungsten alloy during annealing, and inhibit grain growth. When the annealing temperature is lower than 1200 °C, the compressive strength of tungsten alloy remains unchanged, while the failure strain increases. After annealing at 1500 °C, the strength and failure strain of tungsten alloy decreased by 18.9% and 35.7% respectively. In order to obtain excellent strength and toughness, annealing at 1100–1200 °C for 1 h can be chosen for W-1.5ZrO₂ alloy.

[en] Highlights: • ZrO₂ doped molybdenum alloy was prepared by liquid-liquid doping method. • The improvement of yield strength by ZrO₂ is mainly reflected in grain boundary strengthening. • The addition of ZrO₂ accelerates the cyclic hardening/softening. • ZrO₂ can improve the total fatigue absorption energy and fatigue life of molybdenum alloy. -- Abstract: Pure molybdenum and ZrO₂ dispersion strengthened Mo alloy were prepared by liquid-liquid doping method. The effects of adding ZrO₂ on their microstructure and properties were investigated by tensile test and low cycle fatigue (LCF) test at room temperature, and the fracture mode and energy absorption were analyzed. The research shows that ZrO₂ can refine the grain size and increase the recrystallization temperature of molybdenum alloy. The enhancement of yield strength by ZrO₂ is mainly reflected in grain boundary strengthening. The tensile fracture mode is related to grain size, and changes from transgranular fracture to transgranular-intergranular fracture with the decrease of grain size. At the initial stage of the cycle, the increase of strain amplitude changes the cyclic hardening into cyclic softening, and the addition of ZrO2 accelerates the cyclic hardening/softening. With the increase of strain amplitude, the loading energy and absorption energy of a single stable cycle increase, while the unloading energy is basically unchanged. ZrO₂ can increase the total fatigue absorption energy of molybdenum alloy at the same strain amplitude, and the single cycle absorption energy is lower than that of pure Mo, thus increasing the fatigue life.

[en] Highlights: • A Novel high-density iron-tungsten alloy (FWA) was developed by adding W into DT300 steel. • Microstructure of FWA is characterized by Fe₇W₆ and nano Fe₂W particles distributed in -Fe matrix. • The hardness and tensile strength of FWA are 705.63 HV and 1267.67 MPa, respectively. • The specific strength of FWA is 1.8–4.0 times higher than that of tungsten heavy alloys. -- Abstract: This paper develops a new type of high-density iron-tungsten alloy (FWA) with high hardness and tensile strength by adding 15.6 wt% W into DT300 steel. The microstructure of FWA is characterized by separated network-like Fe₇W₆ around the grain boundary of -Fe matrix and nano-scale fine Fe₂W particles are evenly distributed in the -Fe matrix, with some dispersive SiO₂ particles. The new FWA has higher elastic modulus, micro-hardness, and tensile strength compared to DT300 steel. The micro-hardness and tensile strength of the FWA are 716.6 HV and 1267.7 MPa, which are approximately 18.1% and 6.5% higher than those of DT300 steel, respectively. The specific strength of new FWA is 1.49∗10⁵ (N/m²)/(kg/m³), which is 1.8–4 times higher than that of tungsten heavy alloys. The high strength of FWA is attributed to the strengthening of the multiscale iron-tungsten intermetallic compound.

[en] The (0 0 0 1) sapphire samples are irradiated with 60 keV helium ions at the fluences of 5 × 10"1"6, 1 × 10"1"7and 5 × 10"1"7 ions/cm"2 at room temperature. After implantation, two broad absorption bands at 320–460 and 480–700 nm are observed and their intensities increase with the increasing ion fluence. The grazing incidence X-ray diffraction results indicate that the {0 0 0 1} diffraction peaks of sapphire decrease and broaden due to the disorientation of the generated crystallites after ion irradiation. The microstructure evolution is examined by the scanning and transmission electron microscopes. The surface becomes rough because of the aggregation of helium bubbles and migration towards the surface. There is a lattice expansion up to ∼4.5% in the implanted area and the lattice distortion measured from dispersion of (1 1 0) diffraction is ∼4.6°. Such strain of crystal lattice is rather large and leads to contrast fluctuation at scale of 1–2 nm (the bubble size). The laser induced damage threshold (LIDT) is investigated to understand the effect of helium ion beam irradiation on the laser damage resistance of sapphire components and the results show that the LIDT decreases from 5.4 to 2.5 J/cm"2 due to the absorptive color centers, helium bubbles and defects induced by helium ion implantation. The laser damage morphologies of samples before and after ion implantation are also presented