Search

Non-metallic inclusions and zyglo indications frequently occur in the superalloy castings produced through the traditional vacuum gravity investment casting process, particularly in components with thin-walled and complex structural features. The vacuum-assisted low-pressure casting (VLC), a type of counter-gravity casting (CGC) method, has been developed to minimize non-metallic inclusions and zyglo indications in superalloy castings. Rectifying frames for gas turbines made from K446 alloy were produced semi-continuously using the VLC process and subsequently evaluated through tensile testing, chemical composition analysis, X-ray diffraction, and zyglo penetrant inspection. The results indicate a roughly 10% improvement in tensile strength at 800 °C compared to gravity casting. Moreover, no significant changes are observed in the chemical composition of the alloys from the beginning to the end of a casting campaign, indicating that the developed VLC process is viable for the engineering-scale production of superalloy castings. Compared to traditional vacuum gravity casting (GC) method, the application of VLC can reduce the numbers of non-metallic inclusions and Zyglo indications in the castings by over 80%. At the same time, it significantly shortens the production time by 3 to 5 days.

Based on STL (stereo lithography) format file and with Microsoft Visual C++6.0 programming language, a 3D printing slicing software appropriate for the surface strengthening of the parts has been developed, which includes three functions: 3D model import, model slicing and data export. Through the grouping of STL model triangle facets before slicing, the judgment times of the relationship between the triangle facets and the cutting planes are reduced, and the slicing efficiency is improved. Aiming at the fact that the surface should be strengthened when the part is formed by using of 3D printing process, the function of identifying and marking the surface of the geometric entity is accomplished in the slicing software, which can strengthen the surface of the part according to the user’s requirements. The developed slicing software can provide an entity slicing file for 3D printing equipment. The related functions can be adjusted and improved according to user’s needs, which makes the software convenient and flexible to use.

Fused corundum is a rather promising raw material for preparing an alumina-based ceramic core due to its excellent high temperature resistance and chemical inertness. In this study, alumina-based ceramic cores were prepared using fused corundum as the matrix material, and the effect of varying silica powder contents on the properties of the alumina-based ceramic cores, including the sintering shrinkage, the flexural strength, and the high temperature deformation was investigated. The mineralization mechanisms of the silica on the alumina-based ceramic core were also analyzed. The optimum addition amount of silica in this experiment is 8% in weight. At that moment, the aluminum-based core has both a low sintering shrinkage coefficient of 0.66% and better properties: the room temperature flexural strength is 22.19 MPa, the high temperature flexural strength is 21.54 MPa, the high temperature deformation is 0.93 mm, and the residual flexural strength is 47.41 MPa.

In this work, some important factors such as ceramic shell strength, heat preservation temperature, standing time and withdrawal rate, which influence the formability of directionally solidified large-size blades of heavy-duty gas turbine with the liquid metal cooling (LMC) process, were studied through the method of microstructure analysis combining. The results show that the ceramic shell with medium strength (the high temperature flexural strength is 8 MPa, the flexural strength after thermal shock resistance is 12 MPa and the residual flexural strength is 20 MPa) can prevent the rupture and runout of the blade. The appropriate temperature (1,520 °C for upper region and 1,500 °C for lower region) of the heating furnace can eliminate the wide-angle grain boundary, the deviation of grain and the run-out caused by the shell crack. The holding time after pouring (3-5 min) can promote the growth of competitive grains and avoid a great deviation of columnar grains along the crystal orientation <001>, resulting in a straight and uniform grain structure. In addition, to avoid the formation of wrinkles and to ensure a smooth blade surface, the withdrawal rate should be no greater than the growth rate of grain. It is also found that the dendritic space of the blade decreases with the rise of solidification rate, and increases with the enlarging distance between the solidification position and the chill plate.

In order to improve the discharge capacity and cyclic life of Mg–Co-based alloy, ternary Mg45M5Co50(M=Pd, Zr) alloys were synthesized via mechanical alloying. TEM analysis demonstrates that these alloys all possess body-centered cubic (BCC) phase in nano-crystalline. Electrochemical experiments show that Mg45Zr5Co50electrode exhibits the highest capacity (425 mA·h/g) among the Mg45M5Co50(M=Mg, Pd, Zr) alloys. And Mg45Pd5Co50electrode lifts not only the initial discharge capacity (379 mA·h/g), but also the discharge kinetics, e.g., exchange current density and hydrogen diffusion ability from that of Mg50Co50. It could be concluded that the electrochemical performances were enhanced by substituting Zr and Pd for Mg in Mg–Co-based alloy.

As a new method, liquid-metal cooling (LMC) process is used in manufacturing industrial gas turbines (IGT) blades. Numerical simulation is an effective way to investigate the grain’s growth and morphology, and optimize the process. In this paper, mathematical models for heat dynamic radiation and convection boundary of LMC process is established to simulate the temperature fields. Cellular Automaton (CA) method and KGT growth model are used to describe the nucleation and growth. Simulation results and experimental results are compared. The mushy zone and microstructure evolution are studied in detail. This study indicates that simulation and experimental results agree very well with each other. The withdrawal rate has an important influence on the shape of mushy zone and growth rate of the grain directly. A concave mushy zone is formed and the grain tends to convergent under an excessive high of withdrawal rate. But, the mushy zone has a convex shape and the grain is divergent under a smaller withdrawal rate. A variation withdrawal rate (from 2mm/min to 9mm/min) is found to obtain smooth mushy zone, which improves the parallelism of grain and produces high quality IGT blades.

A lead-free piezoelectric material with ultra-high properties, Ba(Ti0.8Zr0.2)O3–x(Ba0.7Ca0.3)TiO3(BZT–xBCT) nanocrystals was synthesized viaa sol–gel method, and the corresponding thin films were also deposited on Pt/Ti/SiO2/Si substrates by a spin-coating approach. The BZT–xBCT thin film exhibited a high remnant polarization of 22.15 μC cm−2with a large coercive field of 68.06 kV cm−1. The resultant gel is calcined at various elevated temperatures and studied with FTIR/XRD/Raman/DSC-TGA/AFM/SEM techniques for gel composition, crystallization, phase transition, thermochemistry and the morphology of the film. Although the room temperature crystal structure of the BZT–xBCT nanocrystals appears to be a standard perovskite structure by conventional X-ray diffraction (XRD), Raman spectroscopy demonstrates the presence of non-centrosymmetric regions arising from the off-centering of the titanium (zirconium) atoms. The Raman spectra findings demonstrate the degree by which the tetragonal phase grows with the increase of calcining temperature in BZT–0.5BCT, and the characteristic ferroelectric–ferroelectric phase transition in BZT–xBCT while going through the MPB process. The structural and constituent evolution for the conversion process from gel to ceramic, as well as the formation mechanism of the BZT–0.5BCT crystallite, were also elucidated.

abstract: Objective: To evaluate the efficacy and safety of Shugan Yiyang Capsule (SGYY) in treating psychogenic and mild arteriogenic erectile dysfunction (ED) of Gan stagnation and Shen deficiency Syndrome type with or without blood stasis.Methods: A multi-centered, randomized, double-blinded, placebo-controlled trial in 304 patients was conducted by dividing them into 3 groups, who received respectively SGYY (n = 102), placebo (n = 101) and Suoyang Bushen capsule (SYBS,n = 101), 1. Og taken three times a day for 4 weeks. Besides, 205 patients were arranged in an open-label study and treated with SGYY l.0 g taken three times a day for 4 weeks. The total effective rate, total remarkably effective rate, erection recovery rate tested by penis hardness test ring, time taken for improving erection among groups, as well as therapeutic effect between psychogenic ED group and mild arteriogenic ED group were compared. Adverse reactions related to SGYY were recorded. And a 3-month follow-up study was conducted on 105 cured patients.Results: The trial was completed in 500 patients. The total effective rate and total remarkably effective rate in the SGYY treated double-blinded group were 88.0% and 64.0% respectively, and those in the open-label group 90.5% and 65.0%, respectively, all significantly higher than those in the placebo (21.0%, 6.0%) and SYBS groups (60.0%, 29.0%),P<0.01. At the same time, the erection recovery rate and improving time in SGYY group were significantly better than those in other groups (P<0.01). No adverse reactions related to SGYY were found. The successful rate of potency to have intercourse within 3 months was over 80% (100 patients out of the 105 cured patients).Conclusion: SGYY was an effective and safe treatment for patients with psychogenic and mild arteriogenic ED of Gan stagnation and Shen deficiency Syndrome type with or without blood stasis, especially for psychogenic ED patients.