Advanced Materials Research Vol. 1096

Abstract: In order to improve the microstructure evolution modeling of dynamic recrystallization (DRX) in agreement with physical experiment, a modified Monte-Carlo (MC) Potts model for simulating DRX process was proposed in this paper under the consideration of the inhomogeneous stored energy distribution related to grain sizes, the nucleation criteria related to critical dislocation density, the site energy change related to grain preferred-growth, the combination of macroscopic thermo-mechanical parameters and microscopic material parameters, and the relationship between MC calculation steps and real DRX time. The results show that the modified model can better simulate the basic characteristics of dynamic recrystallization of metallic materials during forging, which the recrystallized grains nucleate mainly in the deformed regions with high stored energy and preferentially grow up by merging adjacent deformed grains with high stored energy.

Abstract: In this paper, from the standpoint of Raman spectrum research aspect in material science, Raman spectrum analysis of graphite and diamond microcrystal retained by gallium phosphide nanoparticles is introduced. We found that molecular configuration of basic fuchsin adsorbed on gallium phosphide nanoparticles through experiments. Based on these, Raman scattering is used for analyzing basic fuchsin adsorbed on surface of gallium phosphide nanoparticles. Moreover, we discuss the corresponding meanings of agglomeration phenomenon from the perspective of material.

Abstract: For the forging with complex shape, the preform design is a difficult problem in the process and die design. It has an enormous influence on the quality of the forging. In this paper, combining with the FEM, the Ant Colony Algorithm was used for the preform optimization design. The general Ant Colony Algorithm was improved to fit for the multivariate continuous function optimization. The preform die shape was represented by B-spline and the coordinates of the control point of the B-spline were taken as the optimization design variables. The optimization program was developed. Finally, aimed to decrease the material cost of the forging, the preform optimization of a typical H-section forging was obtained using the self-developed program. The optimization results show that the improved Ant Colony Algorithm is suitable for the preform optimization design of forging.

Abstract: A formulation using the deviatoric stress and the continuity equation is extended to the analysis of the dynamic response of functionally graded materials (FGMs) subjected to a thermal shock by smoothed particle hydrodynamics (SPH), in which temperature dependent properties of materials are considered. Several dynamic thermal stress problems are analyzed to investigate the fluctuation of thermal stress at the initial stage under three types of thermal conditions, with the addition of two kinds of mechanical boundary conditions.

Abstract: Based on the large-area aging and cracking phenomena of Liquid Silicone Rubber (LSR) composite bushing sheds occurred in power grid, the research has been performed on LSR composite bushing sheds energizing for many years By using the methods of Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG) analysis, the authors analyze different parts’ aging properties, microstructures and composition changes of LSR bushing sheds. The experimental results show that the natural environment may be one of the important factors that cause the LSR aging, gradually from the surface to the interior, there are no new groups generated in the process of aging, but the long chain content, the crosslinking degree and the side chain methyl number of LSR decrease obviously, and along with the aging aggravation, the organic composition content in LSR reduces gradually. This research poses great reference significance for better understanding aging mechanism of LSR, scientifically evaluating its lifetime, and guiding scene operational maintenance.

Abstract: MnZn soft ferrite materials with NiO-CoO dopant are prepared by conventional oxide technique.The influences of CoO and NiO addition on the microstructure and magnetic properties of low-loss and high Bs MnZn ferrites are investigated. The present results show that MnZn soft ferrite materials with CoO addition of 0.1wt% and NiO addition of 1.28wt% possess both homogeneous grains and high saturation magnetic flux density. The lowest loss point is located at 100°C. The valley point of power loss shifts to higher temperature with increasing of NiO dopant. The power losses decrease and sintering density increases with increase of CoO addition. The sintered MnZn ferrite materials based upon a specific sinter curve possesss excellent comprehensive properties: μi=2198 , Pcv=319 kw/m3 , Bs=540mT (T=25°C), Bs=451mT (T=100°C).

Abstract: The present thesis made a research to evaluate fatigue crack growth rate subjecting to corrosion and cyclic fatigue loading, with the effect of load frequency on fatigue taken into account. A modified Paris’ law based model is proposed. An exponential modified expression of proportional parameter account for fatigue frequency is proposed based on the obvious fact that low frequency loading will lead to long fatigue life, thus prolong interaction time between corrosion media and specimen which will favor for crack propagation. Loading frequency higher enough will shorten that time, thus influence of corrosion will be significantly weaken, close to pure mechanical fatigue. Crack growth rate prediction from proposed formula is proved to be in good agreement with experimental results for steadily extended corrosion fatigue crack.

Abstract: Automobile wheel of A356 alloy was cast by low pressure casting process. The effect of heat treatment process on microstructures and mechanical properties of A356 alloy cast was discussed. The results indicated that optimal parameters of heat treatment process for A356 alloy included solution temperature of 535°Cand holding time of 4.5hours, aging temperature of 145°Cand holding time of 4hours. Ultimate strength of A356 is 270MPa and elongation rate is 10%. Meanwhile, the microstructure has been apparently improved. The eutectic silicon particle became more spheroidal and distributed uniformly in matrix.

Abstract: Ordered mesoporous carbons are synthesized by using the triblock copolymer F127 (EO₁₀₆-PO₇₀-EO₁₀₆) and diblock copolymer PDMS-PEO (DMS₃₂-EO₂₀) as co-templates. KOH is utilized to improve the surface area and tailor the pore texture of the ordered mesoporous carbon. KOH activation significantly increases the surface area of mesoporous carbon due to the generation of micropores in mesopore walls. The obtained activated mesoporous carbons have high surface area (1592 m² g^-1) and large pore volume (0.79 cm³ g^-1). The activated carbons also exhibit improved electrochemical behavior with a specific capacitance of 218.9 F g^-1 at the current density of 1 A g^-1, excellent rate performance and good cycling stability, revealing a promising application in supercapacitors.

Abstract: In this paper, we optimized the geometries the π-lithium bond complexes between three π-bond-containing compounds, ethylene, acetylene, benzene, and amido-lithium have been calculated at DFT-D3/6-311++G**, MP2/6-311++G** and QCISD/6-311++G** theoretical levels. All the equilibrium geometries were confirmed to be stable state by analytical frequency computations. The calculations showed that all the bond lengths of the electron acceptors increased obviously and the red shift of N-Li stretching frequency occurred after complexes formed. The calculated binding energies, ΔE^tot, of the four complexes are-38.11, -41.05 and-45.02 kJ·mol^-1 via the DFT-D3 method, respectively. Natural bond orbital theory analysis revealed that the three complexes were all formed with π-s type lithium bond interaction between three π-lithium bond donor molecules.