Advanced Materials Research Vols. 399-401

Abstract: 20CrMnTiH is widely used as gear steel because of its good hardenability. Based on the Taguchi technique, an L9 orthogonal array was arranged, and the three main process parameters were deformation temperature, strain rate and strain, and their levels were in the range of 850oC~1050oC, 0.1 s^-1~10s^-1 and 0.2~0.8 respectively. Nine hot compression tests were carried out on a GLEEBLE 1500 simulator, and the stress-strain curves and microstructures were investigated. The experimental results showed that deformation temperature was the most significant parameter of flow stress maximum followed by strain rate and strain, and the impact significant degree of on the grain size after compression was shown in the following: deformation temperature > strain > strain rate.

Abstract: Tea saponin (TS), a representative tea seed-derived biosurfactant, was effective in promoting the uptake of Cd from soil by corn (Zea Mays L.). The concentration of Cd in roots increased with the growth of corn, while for shoots, concentration of Cd increased rapidly at the beginning and reached the maximum in a short period and then gradually decreased against the uptake time. Over a 5 day growth period, Cd concentration was 116.9 mg/kg in roots and 104.19 mg/kg in shoots which were both about 1.6 times as that without TS. In addition, the accumulated Cd in corn was greatly influenced by TS concentrations in shoots and roots, the Cd contents in corn shoots and roots increased with the increasing concentrations of TS added in soil. The higher Cd accumulation in the roots and shoots indicated that TS had the potential in enhancing the uptake of Cd into corn in the concentration ranged 25-200 mg/kg.

Abstract: The finite element analysis was applied to evaluate the respective influences of die geometry and process conditions on plastic strain distribution for β-titanium (Ti-13V11Cr3Al) during the equal channel angular extrusion. It was found that optimum ECAE die geometry is strongly material dependent. Optimal strain homogeneity in the Ti-13V11Cr3Al alloy may be achieved at r (inner radius) =5mm, R (outer radius) =3mm. The equivalent plastic strain increases with increasing friction coefficient. And the better homogeneity of the equivalent plastic strain distribution can be achieved when m=0.1. The faster is the ram speed, the lower is the homogeneity of the equivalent plastic strain distribution. The back-pressure can increase the strain level across the workpiece and prevent the problem of surface cracking induced by tensile stresses. The distribution of the plastic strain is not temperature sensitive between 400°C and 600°C.

Abstract: Grain refinement is quite important for producing 7050 alloy ingot especially in large scale. Low frequency electromagnetic casting (LFEC) process was used to make 7050 aluminum alloy Φ310 ingots and study the effect of electromagnetic field and grain refiner on the microstructure of 7050 alloy ingots. The results showed that both grain refiner and low frequency electromagnetic field can result in some grain refinement of 7050 alloy. However, the low frequency electromagnetic field shows more remarkable grain refinement. For the grain refined alloy by grain refiner, further significant grain refinement can be achieved with the application of low frequency electromagnetic field. The finest microstructure was achieved by combining the applications of both grain refiner and electromagnetic field.

Abstract: The effects of electromagnetic stirring on the morphology evolution of primary phase in semisolid A356 alloy slurry prepared by low superheat pouring and slightly electromagnetic stirring (LSPSES) were studied. The results indicated that the slurry containing globular-like primary phase was prepared by LSPSES, and the electromagnetic stirring within range of stirring power studied had the obvious effect on the morphology of primary phase in the slurry. The morphology of primary phase with finer size slurry was evoluted to globullar-like with increase of stirring power.

Abstract: The structure and work characteristics of the extruder cause the pressure fluctuations at foamed sheet die’s entrance, which at exit seriously affect the quality of sheet planet. In view of this, it is very important to stabilize the pressure at the entrance, but pressure fluctuations arising from complex factors are difficult to solve one by one. After the realization of impact at foamed sheet die’s entrance causing by the pressure fluctuations, a device buffering the pressure fluctuations is designed and CFD software FLUENT is used to analysis of its effect.

Abstract: To study the preparation of Fe³⁺/Ag⁺ co-doped TiO₂ photocatalyst with sol-gel auto-igniting method, TiO2 powder was prepared with TiCl4 as raw material and the photocatalytic activity of doped TiO₂ was examined with methylene blue (MB) as water samples, and a 15w low pressure mercury lamp as light source. Results showed that: the TiO₂ co-doped with 0.02% (molar ratio) of Fe3+ and 0.5% (molar ratio) of Ag⁺ gives the highest photocatalytic activity. The according photodegradation rate constant of MB is 1.33 and 1.10 times of that with TiO₂ and Fe/TiO₂ separately.

Abstract: In this experiment, the effects of hair fibers on friction and wear property, Rockwell hardness and impact strength of friction materials were examined. The results showed that friction coefficient increases and stabilizes and specific wear rates were decrease as the hair fibers were filled and, particularly, 1% of the hair fiber content had a significant effect in the friction material. As temperature was changed, the stability of the friction coefficient of friction materials can be improved, the Rockwell hardness decrease and the impact strengths increase by way of increasing the content of hair fibers. The worn surfaces of friction materials were examined by scanning electron microscopy and wear mechanisms were analyzed. So it’s a kind of quite good non-asbestos friction material.

Abstract: This work presents a research on the static structure and modal analysis of precision grinding machine bed. The solid model is created with 3D design software SOLIDWORKS and analyzed by FEA software ANSYS. In order to alleviate the influence of deformation and vibration on precision grinding machine bed, some factors that can influence mass, max displacement and model frequency ware are analyzed. According to of analysis results, an optimization is carried out to determine the dimension and structure of precision grinding machine bed. Compared to the initial structure, the deformation of the optimal structure is less and inherent frequency is higher.

Abstract: Based on the experimental results that two-dimensional dimpled surface structure arranged in 12-fold quasicrystal lattice could effectively reduce drag, a model of two-dimensional Fraunhofer diffraction wave is built in this paper to simulate and analyse the effect characteristics of disturbed waves which generated by two-dimensional quasicrystal and periodic crystal structure. The simulated results show that the intensity distribution of diffraction peaks with 12-fold quasicrystal structure is more uniform and the intensities of diffraction peaks are much smaller in the streamwise direction than that of other structures, meanwhile along spanwise direction it has less strong diffraction peaks, from which it can realize effective drag reduction.