Tungsten-rhenium Alloys Research Articles

Deuterium retention in displacement-damaged tungsten-rhenium alloys: Influence of rhenium concentration and irradiation temperature

Tungsten (W) samples containing 0, 1, 3, and 5 at.% rhenium (Re) were irradiated by 20 MeV W ions to 0.5 dpa at 290 K and to 0.3 dpa at 1350 K. An additional set of samples was irradiated to 0.5 dpa at 290 K and then annealed at 1350 K. The irradiated samples were exposed to a deuterium (D) plasma at 370 K. D concentration profiles in the samples were measured using D(He3,p)α nuclear reaction analysis. The D binding states in the defects were analysed using thermal desorption spectroscopy (TDS). In the case of irradiation at 290 K, the trapped D concentration monotonically increases with increasing Re concentration: in W-5%Re it is 17% higher than in pure W. On the contrary, for irradiation at 1350 K the trapped D concentration monotonically decreases with increasing Re concentration: in W-5%Re it is 50 times smaller than in pure W. In the case of annealing at 1350 K of the samples irradiated at 290 K, the Re presence yields only up to three times reduction of trapped D concentration compared with pure W. TDS shows that the nature of D trapping sites is different for the irradiations at 290 K and 1350 K. We attribute the reduced D trapping in W-Re alloys irradiated at 1350 K to the reduction of cavity growth caused by the presence of Re.

Design and analysis of sensor structure based on ultrasonic temperature measurement

Abstract Based on the principle of ultrasonic temperature measurement, this paper designs the structure of a waveguide rod sensor with a reflective groove. Using multi-physics field simulation software to conduct acoustic thermal coupling parametric simulation analysis on six different high melting point materials, we obtain the curve functions of the relationship between sound velocity and temperature for the six materials and verify the feasibility of ultrasonic temperature measurement using waveguide rods. Analysis shows that the sensitivity of six alloys to temperature changes is as follows: Ti6Al4V titanium alloy > α-Al2O3 > Inconel693 nickel-based alloy > ThO2 > Tungsten-rhenium alloy > Ta8W2Hf. At the same time, three different shapes of waveguide rods were designed: single groove waveguide rod, multi-zone waveguide rod, and spiral waveguide rod to analyze the impact of temperature measurement accuracy. The research results have important theoretical guidance significance for solving the problem of temperature measurement in high-temperature environments.

The Influence of Rhenium Content on Helium Desorption Behavior in Tungsten-Rhenium Alloy.

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.

High compressive strong-ductile tungsten-rhenium alloy via B4C addition

Tungsten-rhenium alloys with high-temperature strength and creep resistance are widely used in the cutting-edge scientific and technological sectors. However, W-5Re alloy with Re content of 5 wt% shows brittleness at room temperature, limiting its aviation temperature measurement. This work provides W-5Re-xB4C (x = 0∼2.0 wt%) tungsten-rhenium alloys with high compressive performance by introducing B4C ceramic phase and regulating the B4C content. The alloys are composed of W(Re) solid solution, W2B phase and a few W2C. When increasing B4C addition, the grain size of the W(Re) matrix decreases from about 200 μm to 17 μm in W-5Re-2B4C and the content of intermetallic compounds increase to be about 12% in W-5Re-0.5B4C and 58% in W-5Re-2B4C. The W-5Re-0.5 wt% B4C alloy exhibits a high yield strength of 1.19 GPa and compressive plasticity with a plastic strain of 42.50%, while the W-5Re-0.75B4C alloy has a high yield strength of 1.52 GPa and good compressive plasticity of 22.52%, obviously higher than the reported W-5Re alloys. Fine-grain strengthening from the refinement of W(Re) and second-phase strengthening from intermetallic compounds simultaneously enhance the alloys, while good deformability of W(Re) metallic phase contributes to the room-temperature plasticity. This study provides necessary data accumulation and theoretical support for the application of tungsten-rhenium alloys.

Comparative study of microstructural evolution in W-3Re alloy under high-temperature conditions: High heat flux loading versus furnace heating

In tokamak devices, tungsten (W), as the main candidate for plasma facing material, will suffer from the simultaneous challenges of high heat flux (HHF) and neutron irradiation. This study involved annealing experiments on W-3Re alloy using two distinct heating methods: furnace heating and electron beam heating. The evolution of hardness and microstrure of tungsten-rhenium (W-3Re) alloy after isochronous annealing and isothermal annealing has been analyzed and compared with pure tungsten (PW). The recrystallization kinetics of W-3Re alloy have been obtained employing the Johnson Mehl-Avrami Kolmogorov (JMAK) equation. Experimental results showed that recrystallization kinetics during electron beam annealing were faster than those in furnace annealing. This phenomenon can be attributed to the rapid heating process of electron beam annealing, which preserved more deformation energy within the material, thus providing more driving force for recrystallization at high temperatures. Additionally, Re appeared to inhibit grain boundary migration in W-3Re alloy, causing the recrystallization temperature to be approximately 100 °C higher than in pure tungsten, and also resulted in a smaller average grain size compared to pure tungsten. This research provides experimental data and reference for predicting the microstructural evolution of tungsten-rhenium alloy in future fusion reactor environments.

STUDY OF THE INFLUENCE OF THE STRUCTURE OF FIBER COMPOSITES ON THEIR PERFORMANCE PROPERTIES

Purpose. It consists in establishing the influence of continuous fibers and a sufficiently plastic matrix of heat-resistant alloy in the structure of a composite intended for work at elevated temperatures, and providing recommendations on the optimal type of structure to achieve optimal strength of this composite at temperatures of 20...1300 °С.
 Research methods. Theoretical analysis of the possible destruction of products when using continuous fibers was carried out, as well as an analysis of composite samples based on a heat-resistant matrix reinforced with a wire made of tungsten-rhenium alloy. The research was conducted using the metallographic method. The strength of the composite was determined by carrying out tensile tests using the IMASH-20-75 device.
 Results. The regularities of the influence of the structure on the strength of fibrous composites have been established, on their basis it is possible more thoroughly analyze the processes that occur both during the destruction of the composite and during its formation and, if necessary, to adjust them in such a way as to ensure the maximum possible strength of the material as a whole.
 Scientific novelty. The regularity of the effect of the general structure of the composite and the matrix surrounding the fibers on the strength of the heat-resistant alloy – tungsten-rhenium fiber composite is established, which allows quantitative analysis of the influence of structural and technological factors of the forming process on the strength of the specified material.
 Practical value. The work can be useful to designers when choosing the composition of the composite, focusing on the expected mechanism of destruction, as well as to technologists for more productive use of production equipment and reducing the consumption of materials for the production of products.

Rhenium Effect in Thin Films and Wires of Tungsten–Rhenium Alloys

Rhenium Effect in Thin Films and Wires of Tungsten–Rhenium Alloys

Effect of concentration of rhenium and temperature on mechanical properties in tungsten-rhenium alloy: A molecular dynamics study

Effect of concentration of rhenium and temperature on mechanical properties in tungsten-rhenium alloy: A molecular dynamics study

Resolving the sintering conundrum of high-rhenium tungsten alloys

Tungsten-rhenium (W-Re) alloys with high-Re contents are the preferred refractory metal materials in many applications because of the improved ductility and processability over pure W and low-Re tungsten alloys. However, the sintering concurrently becomes increasingly more difficult with increasing Re contents. Here we proposed that the sintering conundrum is caused by the lowered crystal symmetry and the wider dihedral angle distribution when body-center-cubic (BCC) W is alloyed with more hexagonal-close-packed (HCP) Re, which results in inefficient pore removal in the final stage sintering. We showed that the conundrum can be resolved by pressureless two-step sintering (TSS) which suppresses accelerating final-stage grain growth, and our proposal is supported by the data of the critical density ρc that is required to start the second step for successful TSS at different W-Re compositions. Dense ultrafine-grained W-Re alloys with ∼300 nm average grain size and up to 25 wt% Re were successfully produced. Our work demonstrates the unique opportunities offered by two-step sintering to advance the scientific understanding and technological practices in powder metallurgy and related fields.

A Study on Laser Processing of Tungsten-Rhenium Alloys for Divertor Development

Tungsten-rhenium alloys are more attractive due to their excellent characteristics, such as high ductility and improved mechanical properties. They can be expected to become some of the candidate materials for the next-generation of nuclear fusion reactors. We have successfully achieved crack-free laser processing in high-doped tungsten-rhenium alloys using a nanosecond Q-switched Nd:YAG laser system. In addition, the connection between the number of cracks and grain size on different rhenium doping concentrations is also characterized.

A comprehensive study on the metallographic preparation of W-Re samples for high resolution electron-based microscopy

Abstract Modern day rotating X-ray anodes utilize a conversion layer comprised of a tungstenrhenium alloy. The thermomechanical loading of this layer during computed tomography operation introduces various signs of fatigue like cracking, roughening, melting, or microstructural changes. Previous work on preparing tungsten samples primarily considered intact thin films or bulk material. This work focuses on the metallographic preparation of the conversion layer surface, which represents the sample edge in polished cross-sectional cuts. The main goals were minimizing preparation artefacts and maximizing obtainable image quality during electron backscatter diffraction. Twelve preparation methods were compared with regard to edge rounding, chipping, and obtainable image quality. Coating the samples with a thin layer of molybdenum and adding a tungsten sheet for edge stabilization led to vastly improved results. Chemical-mechanical polishing of such a sample gave the most balanced set of considered benchmarks.

Development of a newly compact double-focusing mass spectrometer

In recent years, mass spectrometers play an important role in space missions. Based on this, we introduced a newly developed compact double-focusing mass spectrometer. The MS mainly consists of three parts, that is, electron ionization source, electrostatic and magnetic analyzer, focal plane detector. The ionization source employed two identical tungsten-rhenium alloy filaments to avoid failure of the number one filament. Two analyzers connect in reverse to reduce the size and the focal plane detector detects signals simultaneously. This instrument has a 90° magnetic analyzer with asymmetric structure, which has a magnetic flux density of 0.25T. Results show that the H2 peak width ΔM at 50% peak height (FWMH) is 0.080amu which is less than 0.1amu. That is to say, the developed DFMS has a good resolution capability. Besides, the instrument's mass range is 2–69amu, the physical unit weight is 4.9 kg, the dimension is 247mm × 129mm × 128 mm and the power consumption is less than 30 W.

Temperature-dependent synergistic evolution mechanism of rhenium and irradiation defects in tungsten-rhenium alloys

We have systemically investigated the synergistic evolution of rhenium (Re) and irradiation defects in tungsten (W)-Re alloys under different temperatures and irradiation doses using object Kinetic Monte Carlo method. Our results revealed the underlying mechanism for the transition of Re effect on W from beneficial to harmful during the Re-defects evolution with the increase of irradiation dose, in which temperature always plays a critical role. On the one hand, Re will significantly promote the defect annihilation at low irradiation doses and high temperatures, thereby effectively reducing their sizes and number densities. This is due to the formation of stable Re-SIAs complexes that can be eliminated by the mobile vacancy-type defects, whereas the transition of the migration pattern of SIAs only plays a weak role in the defect recombination in W-Re system. On the other hand, with the increase of irradiation dose, Re will aggregate to form Re-rich clusters or even precipitates. Interestingly, the formation mechanism of Re-rich clusters is also dependent on temperature. At low temperatures, the interstitial-mediated mechanism plays a crucial role in the Re-rich cluster formation, while at high temperatures, both SIA-type and vacancy-type defects will act as the transport carriers of Re to promote their clustering. Accordingly, the critical conditions for the transition of Re from beneficial to harmful and the formation of Re-rich clusters at different temperatures and irradiation doses are given with the help of the phase diagram. Our work presents the temperature dependence of the synergy of Re and irradiation defects in W-Re in fusion-relevant environment, which provides a good reference for the development of radiation-resistant materials and the prediction of W performance in fusion reactors.

Crack-free Nanosecond Laser Processing of Mechanically Enhanced Tungsten-rhenium Alloys

Crack-free Nanosecond Laser Processing of Mechanically Enhanced Tungsten-rhenium Alloys

Pressureless two-step sintering of ultrafine-grained refractory metals: Tungsten-rhenium and molybdenum

• Pressureless two-step sintering of W-10Re and Mo has been demonstrated. • 98.4% dense W-10Re with an average grain size of 260 nm can be pressurelessly sintered below 1200 °C. • 98.3% dense Mo with an average grain size of 290 nm can be pressurelessly sintered below 1120 °C. • W-10Re and W have similar grain boundary diffusivity at the same homologous temperature and similar activation energy. • Mo has more sluggish grain boundary diffusivity and larger activation energy. • Pressureless two-step sintering to be a general method to produce dense ultrafine-grained refractory metals and alloys. The challenge of sintering ultrafine-grained refractory metals and alloys to full density is hereby addressed by pressureless two-step sintering in tungsten-rhenium alloy and pure molybdenum. Using properly processed nano powders (∼50 nm average particle size), we are able to sinter W-10Re alloy to 98.4% density below 1200 °C while maintaining a fine grain size of 260 nm, and sinter molybdenum to 98.3% density below 1120 °C while maintaining a fine grain size of 290 nm. Compared to normal sintering, two-step sintering offers record-fine grain sizes and better microstructural uniformity, which translates to better mechanical properties with higher hardness (6.3 GPa for tungsten-rhenium and 4.0 GPa for molybdenum, both being the highest in all pressurelessly sintered samples of the respective material system) and larger Weibull modulus. Together with our previous demonstration in tungsten, we believe that two-step sintering is a general effective method to produce high-quality fine-grained refractory metals and alloys, and the lessons learned here are transferable to other materials for powder metallurgy.

Study on high-temperature mechanical properties of W25Re alloy

Tungsten rhenium alloy is widely used in aerospace, weapon electronics, and other high-temperature fields. W25Re alloy bars were prepared by powder metallurgy combined with the rolling deformation process. The mechanical properties of W25Re alloy were studied. The results show that rolled W25Re alloy bars have excellent mechanical properties. The tensile strength at room temperature is up to 1650 MPa and the elongation is 15%. As temperature increases, the tensile strength of W25Re alloy decreases rapidly, and the elongation first increases and then decreases. However, at 2000 °C, the tensile strength of more than 200 MPa and elongation of 16% can still be maintained. The fracture morphology shows that the dimples disappear and dynamic recrystallization occurs at 1600 °C and that the grain grows further at 2000 °C. The analysis shows that with increasing temperature, the increasing grain size and decreasing grain adhesion lead to decreasing strength and plasticity at 2000 °C.

A Porous Tungsten Substrate for Catalytic Reduction of Hydrogen by Dealloying of a Tungsten–Rhenium Alloy in an Aqueous Solution of Hydrochloric Acid

Selective dissolution of a tungsten (85 wt.%)–rhenium (15 wt.%) alloy with rhenium in hydrochloric acid at the temperature of 298 K and anodic polarization modes was carried out to develop a porous catalytic substrate and to recycle rare metals. The parameters of the effective selective anodic dissolution of the tungsten–rhenium alloy, including the differences in applied potentials and electrolyte composition, were found. It was established that samples of the tungsten–rhenium alloy possess the smallest average pore size after being exposed for 6000 s. The obtained porous tungsten samples were characterized by X-ray diffraction and scanning electron spectroscopy. A thermodynamic description of the processes occurring during the anodic selective dissolution of a binary alloy was proposed. In the course of the work, the selectivity coefficient was determined using an X-ray fluorescence wave-dispersion spectrometer XRF-1800. The existence of a bimodal structure on the tungsten surface after dealloying was proved.

Surface modification and deuterium retention of tungsten and tungsten-rhenium alloys exposed to deuterium plasma

• Pure W and W-Re alloys with Re concentration of 1, 3, 5 and 10 wt% were exposed to D plasma to various D fluences. • The fluence dependence of surface modifications was observed. • Blistering behaviour of W-Re alloys was analysed by EBSD and FIB&SEM. • The D retention in both types of materials was examined by TDS. Surface modification and deuterium (D) retention in pure tungsten (W) and tungsten-rhenium (W-Re) alloys with Re concentration of 1, 3, 5 and 10 wt.% were investigated after exposure to D plasma with an incident energy of 38 eV/D at about 400 K and various fluences ranging from 7.2 × 10 23 to 2.6 × 10 25 D/m 2 . It is found that blistering depends strongly on the exposure fluence for both W and W-Re alloy samples. When the D fluence is higher than 2.8 × 10 24 D/m 2 , the surface of W is covered by two types of blisters. One type is small blisters (<2 μm), which appeared in groups only on grains with surface orientation close to (1 1 1). The other type is large-sized (>8 μm) and extents over several grains. In the cases of W-Re alloys, only small blisters can be observed on their surface. The blisters on the surface of W-Re alloys preferentially appeared on grains with surface orientation close to (1 1 1). Cross-section views of blisters show that the blisters on W-Re alloys always originate from intra-granular cavities. The small and large blisters on W originate from intra- and inter-granular cavities, respectively. The surface blistering fluence threshold for W-Re alloys is lower than for W. For both types of materials, rupture of blisters occurs if the underlying crack reaches the surface at the edge of a blister. The number of ruptured blisters increases with increasing D fluence. TDS results show that there is an additional high-temperature peak at ∼ 800 K in W-Re alloys. The amount of D released from W and W-Re alloys increases with increasing D fluence. In addition, the accumulation of D in W-Re alloys is not noticeably influenced by the amount of Re doping at the exposure temperature of ∼ 400 K.

Microstructure and Properties of Tungsten Rhenium Alloy Prepared by Laser Sintering

Tungsten alloy with addition of rhenium and tantalum was prepared by laser sintering. Microstructure and properties of the samples were tested by optical microscope, X-ray diffractometer and microhardness tester. Dense tungsten alloy block materials were prepared by adjusting laser beam power and laser spot scanning speed. The oxidation of powder can be avoided by desorption and deoxygenation pretreatment and inert gas protection. Static recrystallization occurred in the laser sintering process.

Thermal diffusivity of irradiated tungsten and tungsten-rhenium alloys

The Japan-US PHENIX project irradiated tungsten materials in the RB-19J capsule experiment in the High Flux Isotope Reactor (HFIR). A gadolinium (Gd) shielding was used to absorb the thermal neutrons and reduce rhenium and osmium generation in tungsten. Pure tungsten and K-doped W-3% Re samples were irradiated at 532 – 662 °C to dose of 0.21-0.46 dpa, with the grain orientation perpendicular or parallel to the disk surface. Thermal diffusivity measurements were performed from 100 °C to 500 °C. Additional measurements followed after annealing up to 900 °C. Irradiated pure tungsten specimens showed similar thermal diffusivity results compared with an unirradiated W-1% Re specimen in another study. The transmutation amount of Re was calculated to be about 0.52% for those specimens that showed good agreement with this study. Specimens irradiated in this study to different doses presented almost the same thermal diffusivity. Annealing up to 800 °C resulted in no recovery of thermal diffusivity. These results show that the contribution of crystalline defects to degradation of thermal diffusivity is quite limited. In addition, the thermal diffusivity of the irradiated specimens was getting close to that of the unirradiated specimens at elevated temperature.