Advanced Materials Research Vols. 750-752

Abstract: The microstructure and corrosion properties of the as-cast Mg-Zn-Ca-Nd alloys were investigated in this study. The results showed that the alloy was mainly composed of α-Mg solid solution and the secondary phases of MgZn, Ca₂Mg₆Zn₃ and Mg₄₁Nd₅. The portion of precipitated phases was increased with the increment of Nd content. Both electrochemical measurement and immersion test indicated that Mg-4Zn-0.5Ca-1.0Nd had the best corrosion resistance in SBF solution. This is attributed to a combination of (1) the uniform microstructure of alloy, and (2) a lower volume fraction of second phases. In the Mg-4Zn-0.5Ca-3.0Nd alloy, the corrosion rate might slow down due to finer dendrite cells were surrounded by the more continuous second phases along the grain boundary and in the α-Mg matrix.

Abstract: In order to improve plastic property of AZ31 alloy tubes at room temperature and expand application of cold rolling process in magnesium (Mg) alloys, solution treatment (T4) and cryogenic treatment of AZ31 tubes obtained by drawing were investigated in this work. The results indicate that T4 can improve the microstructure of the alloy, refine grains and eliminate twins. The optimized T4 parameter is 300 °C for 8 h, in which the average grain size of 12 μm can be obtained and elongation reaches to Max of 16.1% and tensile strength reaches to 242 MPa. Moreover, tensile strength was decreased to 211 MPa, while, elongation was improved to 25.4% by T4+cryogenic treatment at-196 °C.

Abstract: The stress corrosion property of 07/09Cr2AlMoRE and its welding joint were investigated under different conditions. The results showed that the anti-SSC performance of welding joint was lower than that of the plate through the Sc experiment. The martensite and overheated structure appeared owing to the improper control during welding and heat treatment, which resulted in the lower anti-SSC property of welding joint. The temperature and Ph value had important effect on corrosion rate through analysis the data of comprehensive corrosion. The corrosion rate would rise 1 times when the temperature increased 30°C. The corrosion rate was improved nearly by one order of magnitude when the pH value decreased from 6 to 4. The corrosion surface was uniform and no any corrosion pit, which indicated that the microstructure and chemical component was nearly uniform.

Abstract: Intensive melt shearing achieved using a twin-screw machine was applied to the 7075 aluminum alloy melt to investigate its effects on grain refinement. Alloy melt without and with melt shearing was cast in the standard test procedure mould, and the effects of casting temperature, shearing time and shearing intensity on microstructures were analyzed. The results show that the intensive melt shearing exhibits superior grain refinement and remarkable structure homogeneity. Without shearing, the grain size increases significantly with the increase in pouring temperature, while with intensive melt shearing the grain size is finer at all the pouring temperatures tested with a reduced grain size dependence on the pouring temperature. With the shearing time or shearing intensity increasing, the grain size of the equiaxed primary α (Al) phase decreases on the sample microstructures, and the grain distributions trend to become more fine and non-dendritical.

Abstract: For the purpose of studying vacancy effect on physics and mechanics property, authors advance a method of calculating mono-vacancy cell valence construction, and get 5 phase construction factors n_AF andα on electron layer. It indicates that vacancy increase electrical resistivity and intensity, and decrease plasticity, which are consistent with experiments. The paper open out the relation between vacancy and physics and mechanics property on electron layer.

Abstract: A novel polymeric phosphate flame retardant (PFR-P) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphbicyclo [2.2.octane (pentaerythritol phosphate, PEPA), POCl₃ and bisphenol S. Phosphorus was bonded both in the main chain and in the pendant group of flame-retardant polymer molecule, reached a content of 13.1%. And sulfur content was 6.75%. The thermal stability was investigated by TGA, and the results showed that the initiative decomposition temperature was 334°C with 41.1% charring residue at 500°C under air. The high phosphorus and sulfur content contributes an excellent flame retardancy to PC/ABS without a considerable decrease of mechanical properties. It is a potential flame retardant for other polymer systems.

Abstract: As the pre-research of analysis and performance characterization of resin system curing process in space environment, this paper designed the research method for resin system curing process research, and taking epoxy E51 and TDE85 as research objects, did the verifying experiment about the research method in terrestrial environment. The verifying experiment confirmed the feasibility of the research method, and got the conclusion that the results came from DSC and FTIR are not exactly consistent, the method of FTIR is more suitable for curing degree testing in the curing process. The mechanics performance testing showed that the rupture properties of tensile fracture surface of two systems chosen in the experiment evolved from brittle fracture to ductile fracture and the toughness of TDE85-593 was better than that of E51-593.

Abstract: Soft-core/hard-shell polyacrylate latex with different cross-linking degree and shell thickness were prepared by semi-continuous seed emulsion copolymerization .The size, size distribution and morphology of latex particles were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The properties of plastisol were investigated by testing their dynamic viscoelasticity and storage stability as well as the mechanical properties. The results showed that the latex particles always keep regular spherical structure throughout the polymerization process; Dynamic viscoelasticity of plasticized system with different cross-linking degree however had little changed. The mechanical properties of the plastigels could be improved by increasing the thickness of shell.

Abstract: The miscibility of chitosan / methylcellulose (CH/MC) blends was studied by FT IR, wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and scanning electronic microscopy (SEM). The regular changes of FT IR and WAXD spectra of CH/MC blend powder indicated the miscibility of the blends. TGA curves and SEM images of cross-sections of the blends films showed partly miscibility.

Abstract: With the method of two-stage mixing, two different tread rubbers have been mixed in internal mixer under the different process conditions. After the experiments, test the temperature rise of rubber compound, mooney viscosity and carbon black disperisity. Study the effect of process condition change on the temperature rise of two kinds of rubber compounds and analyze the relationships between the rubber temperature rise and mooney viscosity, carbon black dispersity. The study finds that the temperature rise of rubber compound has a relationship with the rotor speed of internal mixer, rubber viscosity and filling factors, but when the temperature rise of rubber compound is steady, the carbon black dispersity of rubber compound also can be steady. After two-stage mixing, carbon black dispersity of rubber compounds have been improved obviously. These results also imply that rotor speed of internal mixer and filling factor are very important to carbon black dispersity of rubber compounds.