Search

W–ZrC composites reinforced with Sc 2 O 3 particles were produced by mechanical milling and subsequent spark plasma sintering. W–ZrC/Sc 2 O 3 composites were exposed to the He ion for 2 h with 50 and 80 eV ion energies and a particle flux of above 10 22  m −2  s −1 performed in a Large-power Materials Irradiation Experiment System (LP-MIES). Results showed that W, Sc 2 O 3 , and ZrC can combine well with one another to form a solid solution. Small amounts of ZrC particles can effectively capture impurity O in tungsten GBs and form nano-sized ZrO 2 particles. After a large He + ion irradiation, serious radiation damage occurred on the sample surfaces, exhibiting “fuzz” structures. With the increasing in He + ion energy from 50 eV to 80 eV, the microhardness of the irradiated regions rose, and pores were formed on the affected area. Besides, agglomerated second-phase groups (primary ZrC with slight Sc 2 O 3 ) tended to distribute outward. [ABSTRACT FROM AUTHOR]

The study of thermal shock resistance during short transient events is crucial to the development of fusion devices. In the current study, reinforced tungsten–boron composites were produced through powder metallurgy and spark plasma sintering at 1700 °C and 44.1 MPa. The microstructure and properties of the consolidated composites were studied through field emission scanning electron microscopy and X-ray diffraction. Laser thermal shock test was performed to study melting behavior and crack formation under single thermal shock loading. Erosion and cracks were observed after thermal shock loading. Crack propagation path analysis involved the following three methods (a) analysis of crack propagation directly through particles, (b) analysis of crack propagation through the interface between particles and matrix, and (c) analysis of crack propagation directly through matrix. Thermal stress primarily influences this phenomenon. [ABSTRACT FROM AUTHOR]

W–3Lu 2 O 3 composites were prepared by mechanical milling and spark plasma sintering. The obtained composites were subjected to He + irradiation experiments. The irradiated samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and measurement of Vickers hardness. Thermal desorption spectroscopy analysis was performed to analyze the samples at different damage levels after Fe 2+ and D + irradiation. Results showed varied degrees of He + damage under different energies. Fuzz structures were observed on the surface of the material after irradiation. TEM results indicated that the existence of these fuzz structures was related to the formation of He bubbles. Amorphous, polycrystalline, and γ-W phases formed in areas where He bubbles existed. The measured Vickers hardness proved that radiation hardening occurred after irradiation. After Fe 2+ irradiation at different damage levels, the total retained deuterium amount of W–3Lu 2 O 3 and pure W differed, and the impact of Fe 2+ radiation for deuterium retention on pure tungsten was greater. [ABSTRACT FROM AUTHOR]

W–15 wt.% Ti alloys were fabricated through mechanical alloying with different milling times ranging from 10 h to 80 h. The powders milled for 10, 30, 60, and 80 h were sintered by spark plasma sintering at 1600 °C. The milled powders and sintered samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy; and their microhardness and thermal conductivity were investigated. Results revealed that the particles underwent welding, fracturing, and rewelding when the milling time increased. The grain size decreased, whereas the microstrain increased from 0.344% at 10 h to 0.543% at 80 h and dislocation density increased with the increase in milling time. However, the WC contamination was induced into the powder after a long milling time, thereby possibly forming the (Ti,W)C 1 − x solid solution with the addition of Ti after sintering. The second phase became uniformly distributed and the W grain size was reduced from 1.48 μm to 0.31 μm after a long milling time. Furthermore, the Vickers hardness increased from 543.05 Hv to 890.30 Hv and thermal conductivity also increased with an increase in milling time. [ABSTRACT FROM AUTHOR]

In this investigation, TiN-reinforced W–Ti alloys were fabricated through spark plasma sintering of milled TiH 2 powders and micro-sized W powders. TiH 2 powder was used to prevent oxidation during milling. X-ray, FESEM, and TEM analyses were adopted to study the microstructures of the powders and sintered samples. As the Ti content increased from 0 wt.% to 4 wt.%, the grain size of the resultant alloy was significantly refined and a more transgranular fracture was observed. The micro-hardness of the alloys significantly increased with addition of up to 4 wt.% Ti and then decreased with further Ti addition. A Ti/TiN solution in which N probably diffused into other Ti lattices during the sintering process was detected by TEM. The effect of He + irradiation was investigated in this work. Samples with 0 and 8 wt.% Ti were exposed to a He + ion beam (He + ion beam flux, 1.2 × 10 22 ions/m 2 ·s; beam energy, 50 eV) for 1 h through the Large-Power Materials Irradiation Experiment System. Results revealed peeling off of TiN particles after irradiation as well as the presence of pores that could induce erosion in the grain boundaries. The sample with 8 wt.% Ti showed no secondary-phase peeling, and only a small density of blisters were found in its W-grain and Ti-rich phases. [ABSTRACT FROM AUTHOR]

Tungsten and its alloys are primary plasma-facing materials in fusion reactors. In this study, pure W and W/TaC alloys and their powders were developed via a powder metallurgical method and a novel wet chemical process, respectively. W alloys with 1, 2, and 4 wt.% TaC were sintered via spark plasma sintering at 1800 °C for 1 min. The sintered samples were characterized using field-emission scanning electron and transmission electron microscopes. TaC particles were found in grain boundaries, which could be crack sources. TaC particles were also found in grain interiors, which changed the crack propagation path, thereby improving material toughness. The microhardness and thermal conductivity of the pure and doped W materials were investigated. The particle microhardnesss increased with the increase in TaC content. The W–1 wt.% TaC alloy exhibited the highest thermal conductivity (up to 183.8 W/mK). [ABSTRACT FROM AUTHOR]

W/steel composites are being developed for potential application in He gas-cooled divertors and plasma-facing components in fusion reactors. In this study, the dissimilar metal joints between W and Fe were fabricated at 950 °C via spark plasma sintering method with Ti foil (Ti–F) and Ti powder (Ti–P) as the interlayer under Ar atmosphere for 5 min at 57 MPa. Microscopic structures of the W/Fe diffusion joints with Ti–F and Ti–P were investigated and compared via field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermal cycling tests were employed to measure the thermal stability of different types of W/Ti/Fe samples. The hardness distribution across joining interfaces was also determined. After thermal cycling tests, a crack occurred along the W/Ti–P interface in the W/Ti–P/Fe samples, whereas the W/Ti–F/Fe samples were intact at the interfaces. Results revealed that Ti–F is more suitable as an interlayer than Ti–P, and the interfaces of the W/Ti–F/Fe samples have better thermal stability than those of the W/Ti–P/Fe ones. [ABSTRACT FROM AUTHOR]

A chemical method was used to synthesize W/TiC composite powder. The obtained powder can achieve near full densification (relative density of 99.0%) after sintering by spark plasma technology at 1800 °C for 3 min. Field-emission scanning electron microscopy and transmission electron micrographs showed that doped TiC nano-particles existed at the grain interior and grain boundary. Transgranular and intergranular fractures can be observed on the surface of the sintered sample. The thermal conductivity of the sintered specimen was 122.89 W/mK at room temperature and has high thermal stability at high temperature. The specimen was uniformly organized on the basis of its microhardness after heat-treated at 1200 °C and 1300 °C. [ABSTRACT FROM AUTHOR]

TiC/W ultra-fine powders were produced by one-step activation and chemical reduction process. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The grain size, relative density and the Vicker hardness HV 0.2 of the bulk sample fabricated by SPS were 3 μm, 98.6% and 471, respectively. The reduced Young's elastic modulus of the sintered W–1 wt.% TiC composites was 382.7 GPa. As the temperature rises from room temperature (RT) to 1100 K, the thermal conductivity of pure W and W–1 wt.% TiC composites decreased with the same trend. However, the thermal conductivity of the samples was both above 120 W/m K at RT. [ABSTRACT FROM AUTHOR]

W–1 wt%Nb/TiC composites were prepared by mechanical milling and spark plasma sintering. Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and thermal conductivity analyses were used to characterize the samples. Results showed that niobium carbide (NbC) formed in the composites. The relative density of the composites has been improved after adding Nb into W–1 wt%TiC. The tensile strength increased as well because Nb has high affinity for impurities such as O, C, and N and can form with these elements hard compounds. The thermal conductivity of W–1 wt%Nb/TiC was also improved, in comparison with that of W–1 wt%TiC. [ABSTRACT FROM AUTHOR]

W–1 wt% Sm 2 O 3 powders doped with highly uniform Sm 2 O 3 were successfully synthesized by a novel wet chemical method followed by hydrogen reduction. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. The FE-SEM and HRTEM analysis, tensile test and thermal conductivity measurements were used to characterize these samples. The grain size, relative density of the bulk samples fabricated by SPS sintering were 4 μm and 97.8%, respectively. The tensile strength values of Sm 2 O 3 /W samples were higher than those of pure W samples. As the temperature rises from 25 to 800 °C, the thermal conductivity of pure W and W–1 wt% Sm 2 O 3 composites decreased with the same trend and the thermal conductivity of both samples was above 160 W/m K at room temperature. [ABSTRACT FROM AUTHOR]

WC-8Co composite powders doped with Y 2 O 3 were prepared by wet chemical method, and the densification of alloy proceeded by spark plasma sintering at 1200 °C, 1250 °C, and 1300 °C. The microstructure of the composite powders and alloys was analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Result showed that the addition of Y 2 O 3 could refine WC particles during carbonization and WC grains during sintering. In the microstructure of WC-Co alloys, Y 2 O 3 solidly dissolved in the body of WC crystal with the form of the second-phase nanocrystal. Moreover, the effect of sintering temperature on WC-8Co cemented carbide doped with Y 2 O 3 was studied. The comprehensive performance of WC-8Co cemented carbide doped with Y 2 O 3 was best at the sintering temperature of 1250 °C with the hardness of 19.64 GPa and fracture toughness of 11.97 MPa m1/2. • WC-8Co-0.5Y 2 O 3 cemented carbides were prepared by wet chemical method and SPS technology. • > Y 2 O 3 refined the particle size of WC during carbonization and retained the grain growth of WC during sintering. • > The addition of Y 2 O 3 improved properties of WC-8Co cemented carbides. [ABSTRACT FROM AUTHOR]

An efficient powder metallurgy route including wet dispersion, high energy ball milling (HEBM) and spark plasma sintering (SPS) was proposed to fabricate carbon nanotube reinforced molybdenum‑hafnium‑carbon (CNT-reinforced MHC) composites. To improve the dispersion efficiency of carbon nanotubes (CNTs) in the molybdenum (Mo) matrix, acid treatment was used to de-agglomerate CNTs. Carbon nanotube/hafnium hydride (CNT/HfH 2) powder prepared by wet dispersion and the powder subsequently milled with Mo through HEBM to fabricate MHC composite powder. The results show that this powder metallurgy process improved the dispersion uniformly of HfC and grain size. The strengthening mechanism of dispersion strengthening, grain refinement, lattice distortion and purification of free oxygen improved the relative density, microstructures and mechanical properties of the CNT-reinforced MHC composites. As a result, compared to other control groups and Mo based composites, the 30 h ball milling time of CNT-reinforced MHC composite (30 h composite) exhibits simultaneous enhancement in relative density, mechanical properties and improvement in microstructure. This work provides a feasible way to fabricate high-performance Mo matrix composites. Unlabelled Image • An efficient powder metallurgy utilizing CNT was proposed to fabricate MHC composite. • This process improved the dispersion uniformity of HfC and grain size. • Simultaneous improvement in microstructure and mechanical properties were achieved in composite. [ABSTRACT FROM AUTHOR]

Pure tungsten and tungsten alloys with 1, 2, and 3 wt.% Lu 2 O 3 were fabricated by mechanical alloying and spark plasma sintering at 1600 °C for 3 min. These samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, Vickers microhardness, thermal conductivity analyses, thermal shock test, and deuterium retention. Results revealed that the microhardnesses of the samples have a similar trend with the relative density. With increased the doped Lu 2 O 3 content, the relative density and microhardness increased and the Lu 2 O 3 particles significantly increased the density and strengthened of tungsten alloy. With increased temperature from 300–1100 K, the thermal conductivity decreased with increased Lu 2 O 3 content. The doped Lu 2 O 3 particles revealed good enhancement effect in the thermal shock resistance and a good influence in the deuterium retention. [ABSTRACT FROM AUTHOR]

“Pure” W was prepared through a powder metallurgy route by using hard alloy (WC–Co) milling tank and balls to mill WO 3 powder, reducing with high purity H 2 , and sintering with spark plasma sintering technique. XRD, SEM, and TEM were used to characterize the phase and phase structures. Results showed that the cobalt tungsten carbide (Co 3 W 10 C 3.4 ) phase was induced from the milling tank and balls. After the “pure” W bulk was exposed to helium ions for 2 h, the cobalt tungsten carbide phase was found to be surrounded by the lattice distortion phase of W, which showed high irradiation resistance. [ABSTRACT FROM AUTHOR]

W–3 wt%Sm 2 O 3 composite powders were formed by mechanical alloying for 5 h. The powders were consolidated by spark plasma sintering (SPS) at 1800 °C to suppress grain growth during sintering. Microstructure and properties of W–3 wt%Sm 2 O 3 composites were investigated by scanning electron microscopy, transmission electron microscopy, microhardness test, and thermal conductivity test. The grain size, relative density of the W–3 wt%Sm 2 O 3 composites were 3–4 μm and 91%, respectively. As the temperature rises from 25 to 800 °C, the thermal conductivity of W–3 wt%Sm 2 O 3 composites increased and the thermal conductivity of the samples was above 170 W/m K at room temperature. [ABSTRACT FROM AUTHOR]

• A spark plasma sintering(SPS) technique is used to bond tungsten(W) and copper(Cu) based on the laser texturing tungsten surface. Five microstructures, namely pristine structure, micropores1, micropores2, microgrooves, and nanoripples, were fabricated on the tungsten surface. • Analyze the influence of tungsten surface microstructure on its mechanical properties through shear performance testing. The results indicate that the microgroove has the best shear resistance. • Thermal fatigue testing of various W/Cu joints revealed that the microgroove sample exhibited the highest thermal shock times. • The thermal diffusion coefficient of W/Cu connected samples was measured by the laser flash method to characterize their conductivity, with the nanoripples sample having the highest thermal diffusion coefficient. In this study, a spark plasma sintering(SPS) technique is used to bond tungsten(W) and copper(Cu) based on the laser texturing tungsten surface. Five microstructures, namely pristine structure, micropores1, micropores2, microgrooves, and nanoripples, were fabricated on the tungsten surface, and the effect of the microstructures on the shear properties, thermal shock resistance, and thermal conductivity of the tungsten/copper joints was investigated. W with the original planar morphology did not form an effective connection with copper, while the W with other surface structures connected well with copper. The results of the shear resistance experiments showed that the micro/nano interface structure significantly improved the shear resistance of W/Cu, where the microgroove structure presented the highest shear strength of 88.19 MPa. It was found that the volume of copper infiltrated into the microstructures had the greatest effect on the thermal shock resistance of the tungsten/copper joint. The highest number of microgroove thermal shock resistance was 297 times. The highest thermal diffusion coefficient of 82.31 mm²/s was obtained for the nanoripple specimens. [ABSTRACT FROM AUTHOR]

In the four temperature ranges of 1300–1600 °C, the diffusion bonding of oxide dispersion enhanced tungsten (ODS-W) and molybdenum hafnium carbon (MHC) alloy prepared by mechanical alloying method was successfully prepared by spark plasma sintering (SPS). In this work, the interface microstructure, mechanical properties and thermal shock resistance of ODS-W/MHC are studied. At above 1500 °C, the W and Mo elements at the ODS-W/MHC interface begin to diffuse, and the diffusion distance can reach 2 μm at 1600 °C. Similarly, the tensile strength of ODS-W/MHC joints is best performed at 1600 °C, with tensile strengths of 425 MPa and 801 MPa at room temperature and 500 °C, respectively. However, as the sintering temperature increased, the hardness of the MHC gradually increased, and ODS-W would recrystallize, resulting in a hardness at the interface between the hardness values of the two substrates. At 1600 °C, the maximum hardness at the sample junction can reach 487 HV. The transient thermal load of the connector during operation is simulated by laser beam and thermal shock experiments are performed on the surface and interface of the ODS-W/MHC connector prepared at different temperatures. Compared with ODS-W, the surface of ODS-W/MHC has no obvious cracks after laser thermal shock, and the cracks generated by the sample interface above 1500 °C have also been greatly improved. It can be seen from CLSM analysis that the height undulation of the surface and interface of ODS-W/MHC is significantly smaller than that of ODS-W, so the ODS-W/MHC prepared at 1600 °C has good thermal shock resistance. • The diffusion bonding ofODS-W and MHC prepared by mechanical alloying and SPS. • At above 1500 °C, the W and Mo elements at the ODS-W/MHC interface began to diffuse, and the diffusion distance reached 2 μm at 1600 °C. • The tensile strength of the ODS-W/MHC joints prepared at 1600 °C at room temperature and 500 °C was 425 MPa and 801 MPa. [ABSTRACT FROM AUTHOR]

● Ultrafine W-(Y 0.9 La 0.1) 2 O 3 composites can be prepared under appropriate temperature and pressure. ● The size of second phase is nanoscale under appropriate sintered condition. ● The dispersed and fine dispersion of second phase can effectively resistance surface damage of tungsten. In this study, W-(Y 0.9 La 0.1) 2 O 3 composite powders are fabricated by means of a combination of wet chemical method and spark plasma sintering. We systematically study the sintering and densification behavior of W-(Y 0.9 La 0.1) 2 O 3 composite powders at different temperatures and pressures. The results indicate that ultrafine tungsten-based composites with a dispersed distribution of (Y 0.9 La 0.1) 2 O 3 particles can be achieved under optimized temperature and pressure conditions. The optimized pressure and sintering temperature for W-(Y 0.9 La 0.1) 2 O 3 composites are identified to be 75 MPa and 1600 °C, respectively. In addition, the surface damage behavior of W-(Y 0.9 La 0.1) 2 O 3 composites induced by the laser thermal shock and helium ion irradiation are also investigated. It is shown that the presence of holes greatly enlarges the helium retention during helium ion irradiation and promotes the melting caused by local overheating during laser thermal shock. We find that the fine-dispersed distribution of (Y 0.9 La 0.1) 2 O 3 particles in the tungsten-based composites can effectively improve the resistance of helium ion irradiation and laser thermal shock. We hope that these findings could provide some guidance and reference for the fabrication of large-sized tungsten-based materials in fusion engineering. [ABSTRACT FROM AUTHOR]

High-strength and high-conductivity copper alloys have a wide range of applications, such as an important electrical contact material. In this work, Cu–Y 2 O 3 composite material was prepared through solid–liquid doping, calcination reduction, and spark plasma sintering. The effect of different yttrium oxide content (1, 3, and 5 wt%) on the microstructure and mechanical properties of the composite was studied. Results showed that the surface of the calcined and reduced copper powder was uniformly covered with yttrium oxide particles. After spark plasma sintering, the relative density of the blocks almost reached 100%. With the increase in yttrium oxide content, the distribution of yttrium oxide transformed from dispersion to agglomeration, and the grain size gradually decreased. There is a good bond between the copper matrix and yttrium oxide, and the particle size of yttrium oxide particles is approximately 150 nm. In terms of mechanical properties, the Cu-3wt.% Y 2 O 3 sample obtained the best comprehensive mechanical properties with strength of 290.1 MPa, hardness of 125.7 HV, and conductivity maintained at a high level of 95% International Annealed Copper Standard (hereinafter called IACS). • Cu–Y 2 O 3 composite was prepared by solid–liquid doping, calcination reduction, and spark plasma sintering. • Yttrium oxide greatly improves the strength and hardness of copper composites. • The dispersion distribution of yttrium oxide helps to improve the electrical conductivity of copper. [ABSTRACT FROM AUTHOR]

In the absence of an intermediate layer, ODS-W (W–2%Y 2 O 3) and copper (Cu) powders were successfully combined by spark plasma sintering (SPS) in the temperature range of 850 °C-980 °C. In this paper, the microstructure of the joints at different temperatures was investigated by SEM, EDS, and TEM, and the phase composition of the bonded joints was studied by XRD. The effects of sintering temperature on diffusion distance and physical mechanical properties were analyzed. The diffusion distances of Cu and W increased as the bonding temperature increased. At 980 °C, no microcracks and pores were formed at the joint of ODS-W/Cu, and the mutual diffusion distance between W and Cu was the longest, reaching 1.3 μm. When yttrium oxide started to emerge near the ODS-W/Cu joint, the diffusion distance between W and Cu increased. In addition, at 980 °C, the ODS-W/Cu connector has a great difference compared with other temperatures, with the tensile strength up to 312 MPa and hardness up to 200 H V. • Diffusion bonding was achieved between ODS-W and Cu without interlayers by SPS. &gt. • Mutual diffusion occurs between ODS-W and Cu, and the diffusion layer is about 1.3 μm &gt. • Y 2 O 3 particles promotes the interdiffusion between W and Cu. &gt. • The ODS-W/Cu joint exhibits excellent mechanical properties. [ABSTRACT FROM AUTHOR]