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To reduce the sintering temperature of liquid-phase sintered conductive SiC ceramics, the SiC nanopowder with Sc2O3 additives was intentionally oxidized by heat treatment in air to enhance the SiO2 content coated on SiC surfaces moderately. Taking advantage of the lower eutectic temperature (1660 °C) between SiO2 and Sc2O3, conductive SiC ceramics were successfully sintered at 1700 °C. The effects of sintering temperature (1700–1900 °C), holding time (1–10 min), and additive content (1–7 wt.%) on microstructural, mechanical, and electrical properties were systematically investigated. The phase composition of as-received SiC ceramics contained Sc–Si–O–C–N and doped β-SiC, without apparent phase transformation of β-SiC to α-SiC. The Vickers hardness, elastic modulus, and fracture toughness of SiC ceramics varied within the ranges of 18.08–22.29 GPa, 269.12–391.16 GPa, and 4.09–7.86 MPa m1/2, respectively. The electrical resistivity of conductive SiC ceramics obtained under different process conditions varied in a small range (1–10 Ω cm). Meanwhile, the low-temperature sintering, phase formation, and evolution mechanisms of electrical properties were discussed in detail. [ABSTRACT FROM AUTHOR]

The background of deep peak-shaving poses demanding requirements for the performance of metal components in thermal power plants. The cracking of the connecting fins on the side wall of the flue seriously endangers the safe operation of the system. Herein, welding simulations were carried out using the finite element method to understand the cracking process of the connecting fins. By changing the welding process and fin size, their effect on stress and deformation was explored. The results showed that increasing the welding rate would decrease the flexural deformation of the flue-side wall. Additionally, the yield range of the connecting fin depended more on width than thickness, and increased with increasing width. As for the relationship between fin size and flexural deformation, the maximum deformation decreased with the increase in thickness, while it first decreased and then increased with increasing width. Overall, the post-welding stress and deformation of the boiler flue side wall exhibited more sensitivity to the fin width compared with the fin thickness and welding rate. This article clarifies the stress distribution status of the connecting fins in the flue side wall under different welding conditions, providing a basis for analyzing its cracking phenomenon, and further providing theoretical guidance for optimizing the structural parameter design of the side wall. [ABSTRACT FROM AUTHOR]

For nuclear power generation as a carbon‐neutral energy source, in‐vessel retention (IVR) must be implemented to maintain the structural integrity of nuclear reactor pressure vessel (RPV) for more than 72 h under severe accidental conditions. This technology requires accurate prediction of creep deformation and life of RPV material being operated under pressure and extremely high‐temperature gradient. The current work develops a simplified deformation‐mechanism‐based true‐stress (DMTS) model for creep behavior/life‐prediction of SA508 Gr.3 steel, a typical RPV material, above the phase transformation temperatures (800–1000°C). This model is used to evaluate the time to specific creep strain (t3% and t5%) and rupture (tr), in comparison with popular empirical methods such as Orr–Sherby–Dorn (OSD) and Larson–Miller (LM). The simplified DMTS model achieves an excellent agreement with the experimental observations. The controlling deformation mechanisms are also discussed by metallurgical examinations, which provide the physical premise for the model development and application. Highlights: A simplified deformation‐mechanism‐based true‐stress (DMTS) creep model was proposed.This model predicted the creep‐strain time and life of SA508 Gr. 3 at 800–1000°C.The prediction accuracy of simplified DMTS was compared with LM and OSD methods.The dominant creep deformation mechanism was dislocation climb‐plus‐glide. [ABSTRACT FROM AUTHOR]

Micro-arc oxidation (MAO) is very effective to enhance the corrosion performance of Mg alloys. However, the micro-pores in MAO coatings provide a channel for the corrosion medium to reach the alloy matrix. In this work, electron beam strengthening (EBS) is performed to improve the microstructure of the Mg alloy and the MAO coating is prepared subsequently to improve the corrosion performance. The crystalline size of the Mg alloy decreases, the roughness improves, and the corrosion resistance increases. Furthermore, refinement of the grain size by EBS improves the discharge in MAO. The noticeable effect of EBS on the microstructure of the coating lies in the improvement of density, such as porosity reduction by 47.8%. The compactness of the coatings also increases significantly, subsequently improving the corrosion resistance. The corrosion mechanism is proposed. [ABSTRACT FROM AUTHOR]

Recently, there has been a lot of interest in the AlCoCrFeNi2.1 eutectic high‐entropy alloys (EHEAs), which can achieve a good balance of strength and ductility. The relationship between the microstructure and mechanical properties of the alloy was established in this study by examining the microstructural evolution during heat treatment of 500–1000°C. The results show that the alloy's microstructure remained unchanged when the heat treatment temperature was lower than 700°C. With further rise above 800°C, the B2II precipitates were inspected in the L12 matrix. Besides, L12II started to be precipitated from the B2 matrix at 900°C. The tensile test results conducted at 20–1000°C showed that both the yield strength and ultimate tensile strength decreased as the temperature rose. As for the elongation, however, it increased dramatically when the testing temperature was over 800°C, being attributed to the dynamic recrystallization. The results obtained provided a fundamental understanding of high‐temperature properties for duplex HEAs. Highlights: The B2II precipitates were precipitated from the L12 at 800°C.The B2II and L12II were precipitated from the L12 and B2 over 900°C.The yield and tensile strength decreased sharply at 20–700°C and slowly at 800–1000°C.The elongation first remained stable at 20–700°C and then increased sharply at 800–1000°C. [ABSTRACT FROM AUTHOR]

The Electrically Excited Doubly Salient Variable Reluctance Machine (EEDSVRM) is a new type of brushless machine designed according to the principle of air gap reluctance change. There is neither permanent magnet steel nor excitation winding on the rotor. The rotor is made of silicon steel sheets, thus the structure of the variable reluctance machine is very simple. There are many optimization methods for this type of machine optimal design, such as novel machine topology optimization, finite element simulation-based optimization, mathematical analysis-based optimization, intelligent algorithm-based optimization, and multiple fusion-based optimization. Firstly, this article introduces the basic structure and working principle of the EEDSVRM and analyzes both its common regularity and individual difference. Then, the different optimization design methods of EEDSVRM are reviewed, the advantages and disadvantages of the different optimization methods are summarized, and the research interests of the optimization design of variable reluctance machines in the future are prospected. [ABSTRACT FROM AUTHOR]

In this work, the DD98M single crystal superalloys were brazed to themselves using a Pd-Si composite filler. The effect of brazing temperature and soaking time on the microstructure and mechanical behavior of the joints was studied. The microstructure and phase constitution in the joint were identified by the SEM and EDS analysis. The results indicated that the joint obtained was constituted by DD98M/zone 2/zone 1/zone 2/DD98M. The zone 1 was primarily made up of the Ni (Pd, Cr, Co) (s.s), Pd4Si, Pd (Ni, Ti, Al) (s.s) and Pd-rich Ni (Pd, Cr, Co) (s.s), while the zone 2 consisted of the Ni (Pd, Cr, Co) (s.s) and Al2Pd5. During the brazing process, increasing the brazing temperature strengthened the fluidity of the liquid filler, which was favorable to eliminating the solidified pores in the brazing seam. Furthermore, a higher brazing temperature would cause the phases in the zones 1 and 2 to be coarsened remarkably. When setting the brazing temperature to 1060 °C, extending the soaking time made the amount of Pd (Ni, Ti, Al) (s.s) decrease, whereas the amount of Pd4Si increased, because the peritectic reaction between the Pd (Ni, Ti, Al) (s.s) and remnant liquid filler was enhanced. Among the brazing process parameters under investigation, the maximum joint average shear strength obtained reached 338 MPa when the joint was brazed at 1060 °C for 30 min. A ductile fracture mode happened during the shear tests under a joining condition. The work performed can provide valuable data to design the single crystal superalloy brazed joint. [ABSTRACT FROM AUTHOR]

In this work, (Au 79 Ni 17 Pd₄) 96 Ti₄ (wt.%) filler alloy was designed and employed to join SiC ceramics. The effects of brazing temperature and soaking time on the microstructure and fracture morphology of joints were investigated. The results show that the joint obtained can be described as SiC/reaction layer/braze/reaction layer/SiC. The reaction layer was composed of TiC and Au (Si, Ti). The wettability of the filler alloy toward the SiC ceramics was analyzed. The braze zone was mainly constituted by Pd₂Si, Ni₂Si, and Au (Ni, Si). A large number of nano-sized TiC particles were distributed within the Au (Ni, Si) layer. The formation mechanism of the braze containing different phases was discussed. The brazing temperature and soaking time had a significant effect on the reaction layer at the SiC/braze interface and TiC particles within the Au (Ni, Si) layer, while they showed a negligible effect on the Pd₂Si and Ni₂Si within the braze. The inherent reason was also clarified in detail. The joint fractography indicated that a good bonding was achieved between the filler alloy and SiC, while joint fracture was primarily induced by the thermal stresses residing after the brazing cycle.