Advanced Materials Research Vols. 146-147

Abstract: Based on the uniaxial and triaxial compression tests of Three Gorges granites，the crack initiation stress under different confining pressures can be obtained by studying the crack strain curves. The results show that the crack initiation stress changes at the same extent with confining pressure, and is generally located between 25% and 50% of the peak strength. Moreover, the crack initiation criteria and progressive damage model are established, and some beneficial conclusions are drawn. The tension concentration model of elliptic crack can be used to explain cracking mechanism of Three Gorges granite at relatively low confinement, and Three Gorges granite mainly occurs lateral damage in the microfracturing process and exhibits the similar damage evolutionary rule under different confining stress. The damage model can be used to describe the crack propagation process.

Abstract: Li0.99Gd0.01FePO4/C composite was prepared by solid-state reaction, using particle modification with amorphous carbon from the decomposition of glucose and lattice doping with supervalent cation Gd3+. All samples were characterized by X-ray diffraction, scanning electron microscopy, multi-point Brunauer Emmett and Teller methods. The electrochemical tests show Li0.99Gd 0.01FePO4/C composite obtains the highest discharge specific capacity of 154 mAh.g-1 at C/10 rate and the best rate capability. Its specific capacity reaches 131 mAh.g-1 at 2 C rate. Its capacity loss is only 14.9 % when the rate varies from C/10 to 2 C.

Abstract: Two types of welding methods were performed on austenitic 304 stainless steel: laser welding and TIG welding. The differences of the corrosion characteristics of the welded zones from the two welding methods were investigated with electrochemical methods, such as measurement of the corrosion potential, polarization curves, cyclic voltammogram, etc. The Vickers hardness of all laser-welded zones (WM:Weld Metal, HAZ:Heat-Affected Zone, BM:Base Metal) was relatively higher while their corrosion current densities exhibited a comparatively lower value than those which were TIG welded. In particular, the corrosion current density of the TIG-welded HAZ had the highest value among all other welding zones, which suggests that chromium depletion due to the formation of chromium carbide occurs in the HAZ, which is in the sensitization temperature range, thus it can easily be corroded with an active anode. Intergrenular corrosion was also observed at the TIG-welded HAZ and WM zones. Consequently, we can see that corrosion resistance of all austenitic 304 stainless steel welding zones can be improved via the use of laser welding.

Abstract: The effects of titanium modification, which was added along with the pouring liquid in ladles, on the shrinkage porosity and cavity of cast steel ZG45 smelted in intermediate frequency induction furnace were studied. The metal liquid fluidity was measured by casting spiral samples. 0.2 wt.% titanium modification achieved the highest fluidity for steel liquid. Proper content of titanium could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrite, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium modification easily caused mass oxide TiO2, which kept solid phases with high meting point in metal liquid to increase its viscosity and decrease the fluidity. Meanwhile, these solid state titanium compounds enlarged the composition supercooling, so the metal liquid changed from sequential solidification to simultaneous solidification, resulting in inadequate metal liquid feeding, less oncentrated shrinkage cavity and serious shrinkage porosity.

Abstract: The solidification characteristics of silicon steel in twin roll strip casting was studied by physical simulation. The experiments were designed to approximate the solidification conditions of twin roll strip casting. The strips with different cooling rate and different silicon content were prepared. The results show that the solidification structures of the strips with different cooling rate and different Si content are composed of columnar and equiaxed grains, and the solidification structures vary significantly. And with the decrease of cooling rate, the linear contraction rate decreases.

Abstract: A scanning nonlinear dielectric microscopy (SNDM) with an additional electrically conducting atomic force microscope cantilever as a probe needle is adopted to simultaneously observe the surface topographic and domain images of nanocrystalline BaTiO3 ceramics with super-high resolution. The sample exhibits a uniform grain size distribution and the average grain sizes are calculated to be about 30 nm. Some regions are brighter than the others in SNDM image, indicating the existence of ferroelectric domains structure. In addition, P-E hysteresis and piezoresponse loops are found in nanocrystalline BaTiO3 ceramics. The experimental results demonstrate that the SNDM with the function of atomic force microscopy is very useful for understanding domain structures of nanocrystalline ferroelectric materials.

Abstract: This paper applied to relations of the milling time、flakes thickness and diameter size D50 of Al-flakes by High Energy Milling(HEM) use the Benjaminm collision model. Through established of the collision model, the relationship of various technical indicators can be calculated of the flakes, and it can be used to guidance of the preparation and optimize the process.

Abstract: The surface corrosion mechanism of the adaptable and expandable inner bracing screen is introduced, experiment and analysis was made for the surface corrosion with the effect of temperature, chloride ion, calcium ion, pH value, this offer help to the application of adaptable and expandable sand control screen. The results show that surface corrosion rate is expedited with the temperature increase during 30 °C～80 °C, it reach the highest spot at 80 °C and then declined. The screen surface occur dot-corrosion easily in solution which contain chlorine ion, corrosion rate decline with the concentration increase of chlorine ion. Calcium ion can restrain the screen surface corrosion rate. Corrosion rate is decline with the pH value increase during the pH value of 3～6.

Abstract: As an advanced high strength steels, transformation-induced plasticity (TRIP) steel has obtained more and more attentions in automotive body components forming. The TRIP effect of this steel can improve the strength of the material, which results in the spring-back angle is different with that without TRIP effect. In this paper, the spring-back process of U-channel stamping with TRIP effect is studied by deformation energy method, which is based on a constitutive model accompanying strain-induced transformation in strain rate condition. The results have shown that martensite volume fraction distribution in key parts is related to the deformation energy of material, which induces the spring-back angle higher than those without TRIP.

Abstract: Anti-decayed rice straw may be used to reinforce saline soil in inshore of Northern China. Water absorption, maximum elongation and maximum tension of rice straw, including rice straw soaked in seawater, running water and seawater after SH agent has been tested, and anti-decay effect is evaluated based on grey correlative method. The experimental results showed that water absorption of rice straw soaked in seawater and running water increased with soaking time. And maximum elongation and maximum tension decreased with soaking time. The reduction rate of water absorption was the greatest when the rice straw was soaked in seawater after SH agent for 14-day and which had the biggest maximum elongation and maximum tension yet. According to grey correlative method, the relational degrees of water absorption, maximum elongation and maximum tension for 14-day are the biggest. It means that anti-decay effect is the best in this condition. Taking rice straw which soaked in seawater after SH agent for 7-day as example, correlation coefficients of water absorption, maximum elongation and maximum tension increase with soaking time. It indicates that the longer soaking time is, the better anti-decay effect of rice straw is. Evaluating anti-decay effect of rice straw according to grey correlative method and analyzing the laboratory results respectively, they are highly consistent. Grey correlative method is a suitable one for evaluating the anti-decay effect of rice straw.