Advanced Materials Research Vols. 452-453

Abstract: Directional Ni-based superalloy DZ483 is an advanced gas turbine blade material for heavy duty gas turbine application, which has good combination properties. The major research of this paper is studied on DZ483 alloy’s microstructural changes and mechanical property during long-term exposures in service environments. The results showed that: During thermal processing, the size and distribution of γ' phase tends to be more homogeneous in the interdendritic spaces; the γ' phase on the dendrite seem to arrange in designated directions. During long-term exposures, the amount of the γ' phase was decreasing and the foursquare γ' phases gradually became abnormal with the increasing temperature. However, tensile properties of DZ483 have not decreased obviously

Abstract: The thermal diffusivity of green teas has been used as engineering parameter in the design of processes and machines for drying, storing and aeration. The thermal diffusivity of green teas was determined and its changes with moisture content, bulk density investigated. The thermal diffusivity values of green teas decreased from 8.126×10^-8 at 250 kgm^-3 to 5.037×10^-8 m²s^–1 at 550 kgm^-3. The change of the thermal diffusivity of green teas at different moisture content shows that it increased from 8.281×10^-8 at 5.3% db to 12.617×10^-8 m²s^–1 at 70.0% db and from 7.497×10^-8 at 5.3% db to 12.464×10^-8 m²s^–1 at 70.0% db, respectively, as bulk density increased.

Abstract: Hot compression deformation behavior of Ti-6Al-2Zr-3Ni alloy was investigated through thermal simulation tests in the range of 900- 1050°C, with strain rate from 0.001 s-1 to 1 s-1. The results demonstrates that flow stress reaches the maximum quickily, followed by flow softening with the increase of strain in all true stress-strain curves. At a constant strain rate, flow stress will decrease with the test temperature. Moreover, the temperature sensitivity of flow stress reduces largely at temperature between 980 to 1050°C, during which dynamic recovery is the main mechanism for the hot deformed alloy. In addition, flow stress increases with the strain rate. At lower temperature, recrystallization reduces or vanishes at temperature ranging from 900 to 940 °C due to thermodynamics factors.

Abstract: The plastic deformation and brittle fracture damage remained within a certain depth of the abrasive surface of ceramic materials during axial creep feed grinding process, which included much information about damage mechanism and removal mechanism of ceramic materials. The surface morphology analysis showed that the brittle fracture was the main removal mode of grinding surface in addition to some micro-cracks in the affected layer, and cracks were not found in the matrix. Compared with general grinding, only the surface deterioration layer is thicker than general grinding surface, and there is no obvious damage to the workpiece

Abstract: Directionally solidified Ni-based superalloy DZ483 is a kind of potential material for the blade of an advanced heavy duty gas turbine, which has good combination properties. The carbide degradation behaviors of DZ483 alloy during long-term thermal exposures were investigated at different conditions in this paper. The results show that during the long-term exposure, primary carbide will decompose in the form of MC + γ → M23C6 + γ'. Carbide on the grain boundary could be decomposed more easily than intragranular carbide. With the increase of aging time, decomposition could be observed more obviously, carbides on the grain boundary become bigger and the morphology of carbide near the grain boundary tends to be more complex. The fine dispersive particles of M23C6 on the grain boundary will grow up gradually to a thin consecutive chain of carbide with the increase of aging time.

Abstract: In order to improve oxidation/erosion resistance of the T/P 24 steel components used in advanced power plants, chrome carbide coatings were prepared by PIRAC (Powder Immersion Reaction Assisted Coating) on T/P24 at 700-1000°C. Microstructure and phase composition of the obtained surface layers were characterized employing X-ray diffraction and scanning electron microscopy with chemical analysis (SEM/EDS). Results showed that homogenous smooth chrome carbide coatings can be formed on the substrate. Phase composition of the prepared coatings are differs with PIRAC temperatures. Prepared at lower temperatures or short times treatment, Cr23C6, Cr7C3 and Cr3C2 can be detected in the coatings. While, at higher temperatures or longer treatment times, Cr23C6 is subtotal phase of the produced coating. Moreover, the lower the PIRAC temperature is, the more of Cr7C3 and Cr3C2 are. Thermodynamics calculation based on Gibbs free energy is applied to explain phase composition difference of the coatings.

Abstract: In order to improve formability of high strength Al-alloy sheet metal, in this paper, it come up with the synchronized cooling hot forming process. Taking the aluminum alloy of 6016 H18 aluminum alloy, which carried out its technology test by Gleeble3500 hot-mechanical simulator. The process parameters such as deformation temperature T, holding time t and cooling rate v is investigated by the orthogonal test and the microstructure is analyzed simultaneously. The results show that the synchronized cooling hot forming process can be applied to 6016 H18 aluminum alloy, it both improves the formability of 6016 H18 aluminum alloy significantly and obtains the high strength after forming, it can meet the purpose of implementing deformation and enhanced in one process step, the proper combination of process parameters are T=450 °C, t=210 s, v=60 °C/s. Strengthening mechanism is which there is a large number of strengthening phase precipitated from matrix in technology process, the strengthening phases are coarser and the dispersed uniformity is a bit worse compared with that of T4 state.

Abstract: In this study, natural rubber (NR) was treated with sulfuric acid to improve its adhesion properties to polar polymer. T-peel strength tests, scanning electron microscopy, contact-angle measurement (water), Energy Dispersive X-ray Detector were used to analyze the nature of the NR surface modifications which were carried out with sulfuric acid. A noticeable decrease in contact angle was observed on the rubber surface by contact-angle measurements which can be ascribed to the increase of oxidized moieties on the rubber surface. EDX revealed that oxidized moieties were created through treatment with sulfuric acid. The surface modification and mode of bond failure were studied by scanning electron microscopy (SEM). Immersion in sulfuric acid for 15min produced the maximum adhesion strength (10kN/m) and produced a mixed failure mode (interface & rubber failure in the rubber). Treatment with sulfuric acid produced improved wettability as well as chemical (surface oxidation) and morphological modifications (roughness) of the rubber surface.

Abstract: The paper started from the most basic physical law ‘Yang-Laplace equation’, combined with the invariably characteristics of the droplet volume in the Wetting process, established a novel Gravity Model. By numerical simulated, we found that the different of the internal hydrostatic pressure of droplet affected the droplet morphology directly. Otherwise, the paper studied importantly that the droplet gravity generated the pressure on the solid-liquid interface. When the contact angle is more than 172°, the droplet is non-stability in the Cassie states. Only the droplet can keep stability in the Wenzel states.

Abstract: The development of separator is the key issue in the development of lithium battery and further more in hybrid power automobile and BEV Nowadays, the lithium-ion battery separator industry in China falls short of independent innovations and global competitiveness, and is still at its early stages. In addition, the demand of separators in China still relies on import. The nanofibrous lithium-ion battery separators produced by electrospinning bears the quality of high cycle performance, strong thermal stability, and high discharge rate etc, thus can meet the needs of high-standard batteries. In this study, we introduce the new electrospun fibrous separators, present its manufacturing procedures and products properties, analyze the status of the lithium-ion battery separator industry and put forward possible solutions.