Advanced Materials Research Vols. 785-786

Abstract: The phase field model coupling with the concentration field and flow field is used to simulate the dendrite growth during isothermal solidification of Fe-C alloy in a forced flow. The effects of flow velocity on the dendrite growth are studied. The results indicate that with introducing the forced flow, the upstream secondary dendrite arm space decreases, the downstream secondary dendrite arm space increases. As flow velocity increases, the side branch at the upstream regions become bulky and tilt, the side branch at the downstream regions degenerated and even disappear, the length of upstream dendrite arm increases linearly, the length of downstream dendrite arm decreases parabolically. Meanwhile, the solute concentration of upstream dendrite tip increases slowly first, then decreases, the solute concentration of downstream dendrite tip increases monotonously.

Abstract: Microstructure of Mg-9Zn-xAl (x=2,4,6) magnesium alloy was prepared by traditional casting, SIM casting and isolated treatment. The effect of Al content addition on microstructure of Mg-9Zn-xAl was investigated. Results show that Compared with traditional casting, grain size is refined by self-inoculation method casting. Grain size of Mg-9Zn-xAl (x=2,4,6) is 88μm,76μm and 69μm respectively at traditional casting, and is 49.5μm,42μm,35.6μm respectively at SIM casting. With Al content increase, the isolated island-like secondary phase change into semi-continuous network and continuous network, and combination between Magnesium and alloy element decrease accumulation of magnesium atom on the primary phase, so that the growth of the primary phase is prevented.

Abstract: In this paper, the performance comparison between glass ceramics (Zerodur) and silicon carbide (SiC) which are two kinds of common materials used for space optical reflector is carried out, and several lightweight structure forms are analyzed. The oval plane reflector is applied in ultra-low temperature environment of space, take this kind of reflector as an example, its lightweight structure is optimized by CAD, then through finite element analysis, deformation of the planar lightweight mirror is 0.014λ (rms) in gravity condition, and deformation is 0.002λ (rms) in ultra-low temperature of-150 degrees environment. The actual lightweight processing is controled by the CNC system in a graphical way, and using chemical method to eliminate the stress and micro crack generated during processing, its final surface shape precision reaches 0.022λ (rms). Finally, this paper introduces the manufacture method of novel silicon carbide (SiC), and analyzes the current situation and development trends of the spatial lightweight reflector manufacturing technology.

Abstract: Incremental Sheet Forming (ISF) is a new sheet metal forming process characterized by higher formability, product independent tooling and greater process flexibility. A large amount of research work has been spent on ISF process in the last years, but industrial applications are not spreading accordingly. In this paper, numerical simulation, combined with FLD, was performed to analyze the formability of a practical production. Additionally, an actual experiment was done to test and verify the accuracy of numerical simulation analysis results. The high similarity between the analytical prediction values and the measured values indicates it is feasible to predict the formability of the ISF production.

Abstract: Through testing and analyzing Surface micromorphology of protective film and elemental composition and content of vacuum counter-pressure filling AZ91D magnesium alloy by SF₆ mixed gas, the effect of SF₆ concentrations on protective film of vacuum counter-pressure filling molten magnesium alloy was studied. The results show that SF₆ concentrations have greater effect on protective film of molten magnesium alloy. With the increase of SF₆ concentrations, surface micromorphology of protective filmof vacuum counter-pressure filling AZ91D magnesium alloy becomes more continuous and dense. Meanwhile, the mass fraction of F atom of the protective film is increased, and the content of O atom is decreased. Moreover, F/O atomic ratio increases significantly too, so MgF₂ content of the protective film increases gradually. Therefore, protective effect of molten magnesium depends on F/O atomic ratio and MgF₂ content of the protective film. When SF₆ concentrations are greater than 4.8 , protective effect of molten magnesium is good.

Abstract: Acetylation of high amylose (50%) maize starch to high degree of substitution (DS) was synthesised by reacting starch with acetic anhydride using sodium hydroxide as the catalyst. Starch Acetate was dissolved in Dimethyl Sulphoxide (DMSO), the DS of which ranged from 0.8 to 1.8. Ultrafine fibers were made by the method of electrospinning. FTIR, NMR and SEM were used to characterize the structure and surface morphology of the product.

Abstract: Considering the uncertainty and randomness of casing loadings and geometry sizes, performance parameters in deep wells, a kind of calculation method of probability distribution of casing external loading and collapse strength was established. Based on the Monte-Carlo method, the probability distribution of casing strength was simulated under non-uniform external loading conditions. With strength-load interference theory, the calculation method of casing safety reliability was obtained, which can analyzes reliabilities of different types of casing strings subjected different loadings in the dangerous section, and a regional relationship between casing reliabilities and safety factors is established. Results show that when casing reliabilities collapse strengths are in the range of 0.5-1.0, the related safety factors locate from 1.0 to 1.25. Safe reliability analysis can provide references for casing strength designs in deep and super deep wells.

Abstract: The paper is proposed that we can use single factor experiment method and range analysis method to investigate four technological parameters (Melt temperature, Weight loss, Injection time and Gas content) of the technological parameters in the process of microcellular foam injection molding. By investigating the rules and degree which are obtained from the factors influence on bubbles morphology, it is actually meaningful that we can control and improve the bubbles morphology for improving the capability of Microcellular Foam Injection Molding materials.

Abstract: ɸ9mm aluminum alloy rods were prepared by Castex process with on-line solution. The rods were subsequently cold-drawn to ɸ 4 mm wires followed final artificial aging treatment. The microstructures and properties of ɸ 4 mm finish wires were investigated. The results show the tensile strength and equivalent conductivity of the T6-treated wires are 340MPa and 54.21%IACS respectively, it is good competent in the requirement for aluminum alloy-reinforced.

Abstract: T2 red copper plate and DT4C electrical pure iron plate were cladded by explosive welding. Microcosmic analysis and bonding strength of the bonding interface were also studied. Results indicate that the welded zone appears periodical wavy metallurgical interface and obvious element diffusion occurs in the interfacial zone. In addition, no separation happens after the bonding strength test and tension-shear test and the broken zone takes place in the T2 red copper part of the samples, indicating that the bonding strength of the welded interface can get no less than the strength of T2 red copper.