Advanced Materials Research Vols. 562-564

Abstract: In the actual production of iron and steel enterprises, alloy element yield is difficult to predict because it changes with different materials, processes, etc. Then planning weights of raw materials can't be calculated accurately so as to influence raw material cost planning control. Taking raw material attributes, process parameters, and etc. of smelting stage as the influence factors, the prediction model of alloy element yield is built. In order to increase the model’s prediction accuracy, parameter optimization method for support vector regression (SVR) based on ant colony algorithm (ACO) is designed, which optimizes punish parameter, nuclear parameter and sensitive coefficient. The performance of the SVR algorithm with optimized parameters is compared with the grid search algorithm to verify that the former’s performance and efficiency are better. The prediction method of alloy element yield based on the above improved support vector regression is built, whose regression and generalization performance are better compare with BP neural network, so that the relationship between influence factors and the alloy element yield is established. It can predict alloy element yield accurately according to the actual process and provide methods for realizing lean production in iron and steel enterprises.

Abstract: Polyaniline (PANI) is a promising functional polymer in the field of toxic gas detection. In this paper, nano-branched coaxial PANI fibers were grown on electrospun poly(methyl methacrylate) (PMMA) nanofibers by an in situ chemical oxidative polymerization method. The resultant PANI/PMMA fibers were characterized by scanning electronic microscopy and Raman spectrum analysis. The conductivity of an individual coaxial PANI/PMMA fiber is about 2.123 S/cm and that of the conducting PANI coating layer is about 21.8 S/cm. The ammonia sensing properties of the samples were tested by means of impedance analysis. The nano-branched PANI fibers can response significantly to low concentration of ammonia due to large specific surface area, and the sensitivity shows good linear relationship to the ammonia concentration of ppm level. These results indicate that nano-branched coaxial PANI fibers are promising candidate for detection of toxic ammonia gas.

Abstract: Dynamic shearing high strain-rate experiments on three types of titanium alloy have been carried out by using a modified split Hopkinson bar. Microstructure and mechanism for grains refining in adiabatic shear band formed under the condition of high strain-rate were investigated by means of optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). It is shown that the mechanisms for grains refining in adiabatic shear band of titanium alloy mostly consist of three sorts. They are the mechanism of breakdown of elongated grains which due to action of dislocations,and the mechanism of rupture of twins and the mechanism of dynamic recrystallization, respectively. The mechanism of dynamic recrystallization is the universal one for grains refining in adiabatic shear band of titanium alloy. The formation of refining grains is usually a result of combined action of several sorts of mechanisms.

Abstract: In this study, the wear behavior of 9SiCr steel under different treatment with plant abrasive was evaluated by using an abrasive rubber wheel tester. The samples’ microstructures were analyzed by a metallurgical microscope, the samples’ worn surface morphology was observed by using SEM.The results show that: With the increasing of hardness of sample, Its wear resistance is greatly improved. Hardness of laser quenching sample is the highest, wear resistance of it is the best, the second is sub temperature sample. The wear rates and the wear coefficients are proportional to the sliding distance. The Laser quenching samplel display a consistent behaviour with a very low wear rate and a small increase of the wear damage is observed during the abrasive wear tests. The worn surfaces of the three kind samples are characterized by the micro-cutting wear, and no treatment sample is accompanied by fatigue wear mechanism.

Abstract: In this paper, Zn-6Ti master alloy was produced and characterized by XRD and SEM. It was found that α-Al dendritic grains in Zn-25Al alloy were remarkably refined after the addition of Zn-6Ti master alloy, with the size remarkably reduced and the morphology changed from complex dendrite to rose-like or granular (equiaxed particle) structure. Lower solidification temperature of the Zn-Al melt was found to further promote the formation of granular (equiaxed particle) α-Al grain in Zn-25Al alloy with the addition of Zn-6Ti master alloy. The mechanism for the grain refinement is discussed based on the SEM observation of TiAl _3-x Zn_x particles at the center of α-Al grain in Zn-25Al alloy.

Abstract: Oil tubing works as a special pipeline in oil well has the characteristic of high work efficiency and under high loading. Oil tubing failure which commonly happens during the course of oilfield development and production can bring severe economic loss because of the failure accidents caused by the eccentric friction of rods and tubing account for a great percentage. It has a great of significance to study on the fatigue fracture situation and the critical eccentric friction depth of tubing with defects. Oil tubings of J55 material with the specification of Ф73*5.51 commonly used in oilfields were chosen to be the source of semi-ellipse surface crack tensile specimens. Residual life of oil tubing with different eccentric friction percentages was studied through tensile tests. The critical eccentric friction percentage under which the residual life of oil tubing can meet pump detection period was determined, which provides reference for making a reasonable failure standard of tubing. From the tensile test results of the oil tubings of J55 material simulating the condition that the eccentric friction depth accounts for 30% ~ 50% of the wall thickness, the critical friction depth of oil tubing of J55 material is 43.0% of the wall thickness.

Abstract: Nanometer Ni-AlN composite layers were prepared by electrodeposited technology. The optimum technological parameters of nanometer Ni-AlN composite layers were obtained by experiments and analysis. We observed surface morphology and metallurgical structure of composite layers with scanning electron microscope (SEM) and high respective transmission electron microscope (HRTEM). The test results showed that the nanometer Ni-AlN composite layers prepared by proper ultrasonic-electrodeposited technology have better wear resistance and corrosion resistance. And the composite layers consist of AlN particles and nickel grains both nanometer-sized.

Abstract: Based on the finite element method (FEM), we study the elastic constants of double-wall carbon nanotubes (DWCNTs). In the models, the Lennard-Jones potential function is used to consider the Van der Waals' force between non-bond atoms from different layers. The variations of the elastic constants with the diameter and the aspect ratio of the internal layer nanotube are investigated systematically. The computational results indicate that for both the armchair and the zigzag DWCNTs, the elastic moduli are generally lower than those of the single-wall carbon nanotubes with the same chirality as the internal and external layers. With the increase of the diameter and the aspect ratio of the internal layer carbon nanotubes, the elastic constant of DWCNTs will fall to a stable value.

Abstract: With finite element (FE) simulation, we study the buckling behavior of double-wall carbon nanotubes (DWCNTs) under axial compression. In the FE models, linear beam elements and nonlinear spring elements are used to simulate the complex structures and the Van der Waals' force between non-bond atoms from different layers is considered by the Lennard-Jones potential function. The effect of aspect ratio of DWCNTs and double-atoms vacancy on the buckling modes and the critical buckling strains are investigated. The computational results indicate that with the increase of aspect ratio, the critical buckling strains will decrease. For both armchair and zigzag DWCNTs, the critical buckling strains are generally larger than those of the single-wall carbon nanotubes with the same chirality as the external layers and those of the same structures without Van der Waals' force. For defective DWCNTs, the buckling strains of each order decrease by a maximum amplitude of 32.3%.

Abstract: Glass-coated FeCuNbVSiB microwires was annealed in the temperature range of 380 °C to 600 °C. The microstructures and magnetostatic properties of the glass-coated microwires were characterized by X–ray diffraction (XRD), Vibrating Sample Magnetometer (VSM) respectively. Relative complex permeability and complex permittivity was measured by transmission/reflection (T/R) coaxial line method in the frequency range of 2-18 GHz for as-casted and annealed Fe-rich microwires samples. The measured results show that the coercive field of the Fe-rich microwires decrease to 1.54 Oe at 470 °C, and then increase rapidly with the increasing of the annealing temperature. The coercive field and saturation field of the microwire samples increased abruptly with the outgrowth of the Fe-B hard magnetic phase in the Fe-rich microwire samples. The imaginary part of permeability and the natural ferromagnetic resonance frequency decrease for the thermal treatment below 470 °C, and then increase with the annealing temperature up to 530 °C. The change of magnetostatic and microwave electromagnetic properties of the microwires samples with the annealing process come from the change of the anisotropy caused by the internal stress.