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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]

For a long time, people believed that the Pt/C particles aggregation in proton exchange membrane fuel cell (PEMFC) catalyst layer will inevitably lead to lower catalyst utilization. However, our research showed that Pt/C particles aggregation sometimes made catalyst utilization increases. PEMFC catalyst layer microstructure two-phase lattice models, in which we hypothesized that these catalyst layers was composed of C phase (Pt/C particles) and IP phase (the mixture phase of pore and ionic polymer), were used to simulate the effect of Pt/C particles aggregation on catalyst utilization, IP phase tortuosity and cell performance. It was found that when IP phase volume fraction ε < 0.6, catalyst utilization indeed decreased with the increase of aggregation coefficient φ . But, when ε > 0.65, the catalyst utilization of electrodes with Pt/C particles aggregation was larger than the electrode without Pt/C particles aggregation. At the same time, IP phase tortuosity decreased with increasing Pt/C particles aggregation coefficient. In overall consideration of the above factors, the best value of Pt/C particles aggregation coefficient was 5. [ABSTRACT FROM AUTHOR]

A high performance near eutectic Al–Si–Mg alloy profile is developed by micro alloying with 0.1wt.% Ti. The tensile properties of near eutectic Al–Si–Mg alloy with and without Ti in different processing conditions are tested for comparison. Microstructure evolution is observed by optical, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). Results show that the yield strength (YS), ultimate tensile strength (UTS) and elongation of 0.1wt.% Ti alloyed A2 alloy reach up to 193 MPa, 296 MPa and 12.3% respectively, the tensile strength of which is about 50% higher than that of as-extruded base alloy and even stronger than that of the base alloy micro alloyed by 0.1wt.% Zr or 0.1wt.% V. Addition of 0.1wt.% Ti has obvious refine effect on the microstructure of as-cast Al–Si–Mg alloy, however, it has minor strengthening effect on the as-cast mechanical properties. [ABSTRACT FROM AUTHOR]

Fe-based coatings with a high amorphous content were firstly developed by the traditional twin wires arc spray technology. In consideration of empirical rules, including the multi-component system, an optimal concentration of small atoms, negative heat of mixing and an appropriate atom size mismatch among the main components, the cored wires were designed to contain eight elements, which have an optimized atomic volume strain criterion λ n , in range of 0.14–0.21, to render the coatings a high glass forming ability. Then the coatings were prepared using the above-designed cored wires through a rapid arc spray melting and solidification process. Crystalline phases could not be identified from the XRD patterns within the XRD resolution limits, suggesting that the as-sprayed coatings were approximately comprised of fully amorphous phases. With a dense structure and a low porosity of only 2%, the amorphous Fe-based coatings exhibited an attractive combination of high hardness (900–1100 HV 0.3 ) and superior bonding strength (44.9–54.8 MPa). The coating at λ n = 0.21 had the lowest Gibbs free energy difference Δ G , exhibited the largest super-cooled liquid region Δ T x , Lu’s criterion factor γ value and the heat of crystallization (Δ H ) values, which indicating the highest GFA. [ABSTRACT FROM AUTHOR]

Two pieces of plate glass were brazed into a composite of glazing with a vacuum chamber using PbO-TiO 2 -SiO 2 -R x O y powder filler alloys to develop a new type of vacuum glazing. The brazing process was carried out by laser technology. The interface characteristics of laser brazed joints formed between plate glass and solder were investigated using optical microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The results show that the inter-diffusion of Pb/Ti/Si/O elements from the sealing solder toward the glass and O/Al/Si elements from the glass toward the solder, resulting in a reaction layer in the brazed joints. The microstructure phases of PbTiO 3 , AlSiO, SiO 2 and PbO in the glass/solder interface were confirmed by XRD analysis. The joining of the sealing solder to the glass was realized by the reaction products like fibrous structures on interface, where the wetting layer can help improve the bonding performance and strength between the sealing solder and the plate glass during the laser brazing process. [ABSTRACT FROM AUTHOR]

Because inadequate control of the temperature of vacuum glazing may cause changes in form, stress, microstructure, or performance and thereby affect its lifetime, vacuum welding has been adopted to seal the vacuum glazing from the side, and experiments using different sealing temperatures have been executed. The impact of different sealing temperatures on the microstructure of the sealing layer was analyzed to evaluate the combination of material science features on the interface and to reveal the influence of the sealing temperature on the hardness and residual stress of the sealing layer. The results show that a sufficiently high sealing temperature will drive the sealing layer to transform from a hybrid structure to the liquid phase, accelerate the element migration, eliminate pores, stabilize and compact the structure and improve the sealing performance of the vacuum glazing. As the sealing temperature increases, the residual stress and hardness substantially increase. However, when the sealing temperature reaches 460 °C, the residual stress and hardness begin to plateau, and when the sealing temperature reaches 470 °C, no further change can be detected. Therefore, a sufficiently high sealing temperature is beneficial to the bonding of glass and sealing solder and can promote the sealing performance of the vacuum glazing. [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]

Abstract: Low-temperature aging treatments at 120°C for 8h, with and without deep cryogenic pretreatments, were conducted for friction-stir-welded joints of 2024-T351 aluminum alloys. The microstructures and mechanical properties of the welded joints after the above treatments were investigated. Two obvious soft zones were found to be located at the retreating and advancing sides of the heat-affected zone (HAZ) in the as-welded joint. After a single low-temperature aging treatment (LTA), the soft regions close to the base metal in the HAZ almost vanished, while the soft regions close to the thermal-mechanical-affected zone were not significantly affected. Moreover, tensile fracture occurred along the segregation bands of the precipitates in the nugget zone (NZ). This resulted in a decrease in the elongation of the as-welded joint from 74% to 38% that of the base metal. After low-temperature aging with a deep cryogenic pretreatment at 77K, the features of the soft zones were similar to those in the case of the single LTA, but the tensile fracture at the segregation bands in the NZ was inhibited. Consequently, the elongation of the joints improved along with an increase in tensile strength. The possible mechanisms related to the improvement of tensile properties of the joints were discussed. [Copyright &y& Elsevier]

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]