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The ultrafine WC powders with particle size of 0.5 μm were coated by nano Co particles for preparation of the fine WC/Co powder. Then it was mixed with the coarse WC and Co powders, following compacted and sintered in vacuum at 1420 ℃ for 1 h for obtaining the WC-10Co cemented carbides. The morphology, the grain structure, hardness, bending strength and fracture toughness of WC-10Co cemented carbides with the fine WC/Co and ultrafine WC for comparison were investigated by scanning electron microscopy, transmission electron microscope, universal testing machine, etc. The results reveal that the addition of the fine WC/Co has greater influence on the densification of WC-10Co cemented carbides than the ultrafine WC, and can form the dual-grained structure with a mean WC grain size of 2.18 μm, and the WC-10Co with ultrafine WC has a mean WC grain size of 3.57 μm. The WC-10Co with fine WC/Co can reduce grain growth rate and hinder dissolution of the fine grains, resulting in generation of coarse grains with truncated triangular prism and stepped surface by defect-assisted and dissolution-precipitation mechanism. The WC-10Co with fine WC/Co can improve both hardness and fracture toughness, 1131HV30 and 22.1 MPa·m1/2, respectively. Furthermore, with the same hardness of 1131HV30, its fracture toughness is 27.7% higher than linear fitted fracture. The mechanism analysis shows that the addition of ultrafine WC will lead to the formation of abnormal grains, which is not conductive to the performance; while the addition of fine WC/Co simultaneously forms the dual-grained structure and uniform Co distribution structure and reduces the defects in the grains, improves the comprehensive properties.

High-purity and bulk Ta4AlC3 ceramics were successfully fabricated by spark plasma sintering (SPS) and subsequent heat treatment, using the raw materials including TaC and Ta2AlC powders. These raw materials were first synthesized by self-propagation high temperature synthesis from elements tantalum, aluminium and carbon black powders, followed by pressure-less sintering. The as-fabricated bulk Ta4AlC3 was relatively stable when subjected to heat treatment at elevated temperature of 1500°C. Moreover, prolonging the heat treatment time resulted in bigger grain sizes and higher densities of the Ta4AlC3. The flexural strength and the fracture toughness of the Ta4AlC3 fabricated by SPS were found to be 411MPa and 7.11MPa•m1/2, respectively. After the heat treatment at 1500°C for 8 h, the flexural strength and the fracture toughness of the Ta4AlC3 could reach 709MPa and 9.23MPa•m1/2, respectively. The special structural characteristics of the ternary ceramics and the increase of density after the heat treatment are the main reasons for the variation in mechanical properties of ternary ceramics.

More and more attention is being paid to the influence of powder mixing on the mechanical properties and corrosion resistance of WC-based cemented carbides. In this study, WC was mixed with Ni and Ni/Co, respectively, by chemical plating and co-precipitated-hydrogen reduction, which are labelled as WC-NiEP, WC-Ni/CoEP, WC-NiCP and WC-Ni/CoCP, respectively. After being densified in a vacuum, the density and grain size of CP were denser and finer than those of EP were. Simultaneously, the better mechanical properties of flexural strength (1110 MPa) and impact toughness (33 kJ/m2) were obtained by WC-Ni/CoCP due to the uniform distribution of WC and binding phase and solid solution enhancement of the Ni-Co alloy. In addition, the lowest self-corrosion current density of 8.17 × 10−7 A·cm−2, a self-corrosion potential of −0.25 V and the biggest corrosion resistance of 1.26 × 105 Ω in 3.5 wt % NaCl solution were obtained by WC-NiEP because of the presence of the Ni-Co-P alloy. [ABSTRACT FROM AUTHOR]

In this research, thermoplastic polyimide (TPI) were welding via friction stir spot welding (FSSW) in order to evaluate the feasibility of the technology. The welding tool with a tri-flute pin was used for keeping the welding effectiveness. The effect of the rotation speed and dwell time on the microstructure and shear strength was studied. The results shows that the number of gap defects between the shoulder affect zone and the pin affect zone decreased with the increase of the rotation speed. The boundary of the shoulder affect zone and the pin affect zone was no clear when increasing the dwell time from 10 s to 20 s. Long dwell time could increase the mixing time and reduce the materials viscosity, which made the structure was denser. The maximal shear strength was obtained 85.5% of the base materials. The differential scanning calorimetry (DSC) results indicated that the melting behaviour of different regions was no obvious difference. It indicated that FSSW had a feasible and potential technology to join the high temperature resistant engineering plastics. [ABSTRACT FROM AUTHOR]

The development of excellent performance coarse-grained WC-Co cemented carbides has emerged as a hot topic for cutting tools, drills, molds, wear-resistant parts, etc. In this study, the WC powder was coated by Co and La 2 O 3 simultaneously using a new coprecipitation strategy, and its beneficial effects on the densification, microstructure and mechanical properties of WC-10Co was systematically investigated. Firstly, due to the successful introduction of La 2 (C 2 O 4) 3 precursor, the surprising transformation of rod-like loosely CoC 2 O 4 to regular-spherical-like dense one was observed, further inducing the dense and uniform coating of La 2 O 3 with Co on the surface of WC after the H 2 reduction treatment. The addition of La 2 O 3 by this way was found to improve the grain uniformity of WC in the sintered cemented carbide, inhibiting the appearance of abnormally grown grains, and preventing the conversion of Co FCC to Co HCP effectively, which should be ascribed to the segregation of La 2 O 3 on the grain boundary of WC, produced pinning effect and inhibited the dissolution and growth of WC grains. The mechanical properties of coarse-grained WC-Co cemented carbides, including hardness, strength, fracture toughness and elastic modulus were systematically investigated, validating the beneficial effects of Co and La co-precipitation apparently. In general, this study presents a new strategy for enhancing the performance of coarse-grained WC-Co cemented carbides by both powder mixing design and grain boundary tailoring. • A novel is adopted to achieve two-dimensional growth of CoC 2 O 4 • The pinning of La 2 O 3 at grain boundaries tailors the grain distribution of WC • The successful introduction of La 2 O 3 prevents the transformation of Co FCC to Co HCP • The enhanced performance of cemented carbides by both powder mixing design and grain boundary tailoring are obtained [ABSTRACT FROM AUTHOR]

Nickel-based superalloys, owing to their superior resistance against mechanical and chemical degradation, have been widely applied in the aerospace, turbine engine, nuclear reactor, and chemical industries. The microstructure recognition plays a key role in the characterization and design of new superalloys. Although deep learning techniques have achieved satisfactory performance in the microstructure recognition, these methods usually suffer from generalization when the alloy composition or process changed, especially in the high-throughput experiments. In this paper, we propose a semi-supervised deep transfer learning framework for the microstructure recognition of nickel-based superalloys with different compositions and heat treatment procedures. To be specific, we achieve the knowledge transfer of recognition models from one condition (source domain) to another (target domain) by feature distribution alignment (FDA). To avoid the over-fitting, we design a dynamic alignment strategy to achieve the feature alignment based on the label guidance. Additionally, we effectively utilize the unlabeled samples in the target domain and achieve the distribution alignment between the two domains by adversarial training. The experimental results show that our method is superior to the commonly used deep transfer learning methods. In spite of few labeled samples, it can also approach the satisfactory accuracy. Codes are available at: https://github.com/yangchuanwu/FDA. • A semi-supervised deep transfer learning framework for high throughput characterization was developed. • For labeled and unlabeled samples, the feature distribution alignment method is used to transfer knowledge from the source domain to the target. • By learning from small samples, our method can approach the accuracy obtained by training a large number of samples. [ABSTRACT FROM AUTHOR]

In this paper, the safe sealing temperature range of tempered glass was determined to be no more than 300 °C by experiments. On this basis, the feasibility of silver oxide system low melting solder (SOSLMS) used in tempered vacuum glazing (TVG) sealing was explored by sealing strength experiment, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and other test methods. The results of sealing strength experiment showed that the bonding strength of the sealing layer was inversely proportional to the sealing temperature. The bonding strength of the sealing layer in the range of 260 °C–290 °C met the standard requirements (not less than 0.6 MPa) except for the failure of the sample sealing at 300 °C. The observation results of SEM showed that when the sealing temperature was 260 °C and 270 °C, the solder layer had uniform fusion and dense structure, and the sealing layer was tightly bonded. With the increase of sealing temperature, the solder layer began to produce large holes, and there was obvious open gap between solder layer and glass substrate after stretching. The analysis results of EDS showed that the Ag and V elements all diffused into the glass at each sealing temperature, the difference of diffusion concentration and distribution was not significant. The analysis results of XRD showed that when the sealing temperature was in the range of 260 °C–270 °C, there was no crystallization phenomenon in the SOSLMS. When the sealing temperature was in the range of 280 °C–300 °C, Ag 2 VO 2 PO 4 crystals began to precipitate, and with the increase of temperature, the higher the crystallinity was, the greater the crystal content was. In conclusion, in the range of 260 °C–270 °C, the SOSLMS showed good sealing performance, which was suitable for TVG sealing. • A kind of silver oxide system low melting solder was considered to be suitable for tempered vacuum glazing sealing. • The optimal sealing temperature range of silver oxide system low melting solder was 260 °C–270 °C. • The bonding strength of the sealing layer was inversely proportional to the sealing temperature. • The precipitation of Ag 2 VO 2 PO 4 crystals was considered to be the fundamental reason of the reduction of bonding strength. [ABSTRACT FROM AUTHOR]