Advanced Materials Research Vols. 430-432

Abstract: By using biaxial bulge test, it is possible to predict sheet metal forming behavior during hot forming process. The purpose of this study is to obtain materials parameters for elevated temperature forming condition during biaxial bulge test of a nickel base superalloy in hemispherical die. At constant gas pressure, the strain rate in which the metal sheet experiences varies and therefore the strain rate sensitivity can be obtained in a single loading. Biaxial bulge tests on superalloy metal sheet were performed and results are in satisfactory agreement with uniaxial test results at elevated temperature.

Abstract: In this paper, we introduce the notion of vector-valued multiresolution analysis and two-directional vector-valued multivariate wavelet packages associated with an integer-valued dilation matrix. A novel method for constructing multi-dimensional vector-valued wavelet packet is presented. Their characteristics are researched by means of operator theory, time-frequency analysis method and matrix theory. Three orthogonality formulas concerning the wavelet packets are establ- lished. Orthogonality decomposition relation formulas of the space are derived by constru- cting a series of subspaces of wavelet packets.

Abstract: Molecular dynamics simulation method is used to study the [Emim]Cl ionic liquid at the 300K. The density is obtained as 1.1744g/cm3 which agree well with the experimental value (1.186g/cm3) and the relative deviation is only 0.9%. The microstructure, dynamics, and physical chemical properties such as radial distribution functions, diffusion coefficients, viscosity, conductivity of room temperature molten salts [Emim]Cl/AlCl3 with different molar fraction of AlCl3 are calculated. It is shown that the density and electrical conductivity increase, whereas the viscosity decreases with the increasing of molar fraction of AlCl3. The self-diffusion coefficients of [Emim]+, Cl- and AlCl3 increases and the changes of self-diffusion coefficient of AlCl3 is the biggest as to molar fraction increase.

Abstract: The as-cast and semi-solid microstructures of quasicrystal reinforced AZ91 alloys were investigated. The results show that the main phases of as-cast AZ91ZY1 and AZ91ZY2 alloys are all α-Mg, I-phase, Mg17Al12 and Al2Y phase. The grain boundary phases contents increase with increasing Y and Zn contents. The better semi-solid processing technological parameters of AZ91ZY1 and AZ91ZY2 alloys are 580 °C, 30 min and 560 °C, 30 min respectively. The better semi-solid processing temperature of AZ91ZY2 alloy is lower than the one of AZ91ZY1 alloy is mainly attributed to the higher contents of the grain boundary phases in the AZ91ZY2 alloy.

Abstract: In order to find a way which is low cost in preparation of Ti (C,N)/Fe composites. Ti (C,N)/Fe composites were prepared from TiFe (w (Ti)=30%), FeNCr (w (N)=5%,w (Cr)=60%) and toner by Vacuum Hot-pressed Sintering. The effect of sintering temperature on microstructure and performance of Ti (C,N)/Fe composites and the reason of it were studied. The results show that the Ti (C,N)/Fe composites prepared by Vacuum Hot-pressed Sintering have excellent performance, when the temperature was less than 1150°C, shrinkage rate of material was low,and reaction was slow. When the temperature was higher than 1150°C, material shrunk obviously,and reaction became faster, fracture toughness and bending strength rised rapidly at 1150°C-1200°C, rised slowly at 1200°C-1250°C, hardness was maximum at 1200°C.

Abstract: The bake-hardening experiment was carried out for the Ultra-low carbon steel under different pre-strains, and the bake-hardening property is determined. The results are as follows: when the pre-strain is in the range of 0% ~4%, the BH value increases with the increase of the pre-strain; while in the range of 4% ~ 8%, the BH value decreases with the increase of the pre-strain, and when the pre-strain is 4% , the corresponding BH value is higher than others. When the pre-strain is from 8% to 15%, The BH value gets improved with the increase of the pre-strain, and the BH minimum value is corresponding to 8% pre-strain. While the results of Transmission electron microscopy(TEM) analysis shows that the dislocation density of 4% pre-strain is higher than that of 8% obviously, which improves that the dislocation density is the main factor that affects BH value.

Abstract: Raman (4000-95 cm–1) spectra of the recently identified magnetic geometric frustration material – deformed pyrochlore-structure hydroxyl cobalt bromide β-Co2(OH)3Br polycrystalline sample were measured using 10X and 50X microscopic objectives under different laser powers at room temperature. It is found that the obtained Raman bands at these experimental conditions are slightly different from one another. This phenomenon is caused by the so-called local laser heating effect and can help predict the temperature-dependent spectral behavior of β-Co2(OH)3Br around the room temperature. The Raman spectral experiments down to liquid nitrogen temperature (77 K) confirmed this local laser heating effect.

Abstract: A soluble, solution-processable metallopolyyne of platinum (II) functionalized with electron-deficient pyrimidine spacer was synthesized. The spectroscopic and photophysical properties of the polymer was also presented.

Abstract: The RE-7075 Al alloy′s hot rolled sheet was studied in this experiment.The microstructure,over-burning temperature,fracture surface and phase were analyzed by modern materials analytical instruments which include OM(optical microscope),DSC(differential scanning calorimetry), SEM(scanning electron microscope) and XRD(X-ray diffraction),respectively. The results show that there are needle-like or rod-like grains in the SL direction and the fibrous or streamlined grains in the LT direction of hot rolled sheet′s microstructure;The microstructure takes place the phenomenon of over-burning when rolling temperature beyond 480°C; These sheets manifest mainly brittle fracture under the tensile stress; The primary phase of microstructure contain α(Al)、AlLa4、Al2Zn3、AlMgZnCuLa、LaMgZn、AlMg4Zn11 . In recent years,people continued to study the rare earth (RE) and add the RE to the conventional aluminum alloy.So the RE became a hot research because it can improve the properties of materials. The RE-7075 Al alloy is one of the categories and can be widely used as the structural materials of aerospace and weapons industry.With aerospace and the war industry enterprise rapid development in our country, the quantity demand is getting bigger and bigger[1-2].Therefore,it is urgent for us to study a high strength-toughness aluminum alloy material.The aim of RE-7075 Al alloy′s hot rolled sheet was researched in this experiment.The microstructure, over-burning temperature,the fracture mode and phase composition of the sheet were indepth analysised under the rolling process. So these can provide a theoretical basis of the hot rolling process development of science.

Abstract: This paper presents a method called zinc oxalate (ZnC₂O₄) recurrence method to prepare porous zinc oxide (ZnO) films via templating with polystyrene (PS) spheres. Effects of calcination time and temperature, concentration of ZnC₂O₄ in precursor solution on ZnO films were studied. Optimal synthetic conditions and structural features of ZnO films were investigated by DTA, XRD and SEM. Experimental results show that porous ZnO films can be easily prepared by zinc oxalate recurrence methods.