Materials Science Forum Vols. 544-545

Abstract: The hybrid materials with Al-Mg alloy and its composites reinforced with SiC and Al2O3 particles were prepared by conventional powder metallurgy method. The Al-5wt%Mg and composite mixtures were compacted under a pressure of 400MPa and sintered at 873K for 5h. The obtained hybrid materials with Al-Mg/SiCp composite showed the higher relative density than those with Al-Mg/Al2O3 composite after compaction and sintering. In the composite side of hybrid materials, the SiC particles were densely distributed compared to the Al2O3 particles. The hybrid materials with Al-Mg/SiC composite showed higher micro-hardness than those with Al-Mg/Al2O3 composite. The mechanical properties were evaluated by the compressive test. The hybrid materials revealed almost the same value of 0.2% proof stress with Al-Mg alloy. However, their compressive strength was lower than that of Al-Mg alloy, resulting from the fracture occurring along the microinterface between matrix and reinforcements in the macro-interface.

Abstract: This study deals with the dimensional accuracy of outer diameter and geometrical workability in rotary swaged product for various process parameters such as percent reduction in outer diameter and the ratio of thickness to outer diameter of a tube. It is generally known that greater cold strengthening is achieved by rotary swaging process rather than by conventional process such as rolling with respect to the same reduction of cross-sectional area. Percent reduction in the diameter and the ratio are considered and selected as important process parameters because of playing a key role during rotary swaging process. In case of tube under rotary swaging process the ratios have influence on geometrically proper workability without defect for different percent reductions in the diameter. In addition the change of metal flow of workpiece under the swaging process is microscopically and globally observed to analyze the reason why dimensional accuracy of the outer diameter of final product is improved after the rotary swaging process. This work might provide available information for the optimum rotary swaging process.

Abstract: Possibilities of the consolidation process using hot extrusion and subsequent hot rolling were investigated in order to recycle the cutting chips of the aluminum alloy efficiently. For the rolling process, differential speed rolling (DSR) was also applied in addition to normal rolling. Several kinds of cutting chips with different size and cleanliness were collected through turning 6061 aluminum alloy round bars. From these cutting chips, recycled material sheets were produced under various processing conditions via hot extrusion and subsequent hot rolling. Non-recycled material sheets were also prepared for comparison. All samples were characterized by optical microscopy, SEM(EBSP), X-ray texture analysis, tensile test and corrosion test. As a result, it was found that the recycled material sheets produced under optimum processing conditions had smaller grain sizes than those of the non-recycled ones, therefore the mechanical properties and the corrosion resistance of the recycled material sheets were almost comparable to those of the non-recycled ones. Moreover, concerning the DSR processed sheets, the traces of the chip interface, which were clearly observed in the normally rolled ones, almost disappeared, and the appearances were remarkably improved. Then the DSR processed sheets significantly surpassed the non-recycled ones in the tensile properties and the corrosion resistance.

Abstract: Highly purified lignin with 3000 molecule weight, more than 90% purity, was obtained from reed pulp, through the use of organic-solvent-circulation method, a newly lignin separating method. Organic-solvents-circulation method of lignin separation exhibited faint effects on the molecule structure of lignin. Melting lignin showed pseudoplastic characteristics. Lignin blending performed excellent processing properties in molding process.

Abstract: Plasma sprayed coatings have been widely applied in modifying surface properties of metal components. It is also useful to prevent various types of wear, corrosion, erosion and thermal. But the residual stress is still an important problem which can effect the properties of sprayed coating. So it’s necessary to find out the reason of residual stress and the relationship between plasma sprayed condition and residual stress. Plasma spray coating layers with conventional ZrO2 powder was examined to calculate residual stress by X-ray diffraction method with various coating thickness.

Abstract: By controlling texture and grain refinement using ECAP (equal channel angular pressing) process that induces severe shear deformation on materials without change their diameter, strength and ductility of the AZ31 alloy in the bulk form of rod could be enhanced. The original texture was completely replaced by a new texture rotated to have a high Schmid factor during ECAP. The decrease of yield stress after ECAP despite achievement of significant grain refinement was attributed to the strong effect of texture modification. The effect of differential speed rolling (DSR) on mechanical properties of the AZ31 alloy in the form of sheet was examined. Significant grain refinement took place during the rolling owing to introduction of large shear deformation by application of high speed ratio between the upper and lower rolls. Hall-Petch relations of the ECAPed and DSRed AZ31 alloys were compared and notable difference in strength between the two alloys at a given grain size was found and it was attributed to strong texture effect on strength of Mg alloys.

Abstract: Ti50Zr25Cu25 in-situ composite ribbons consisting of metastable β-Ti crystalline phase in an amorphous matrix was studied for its structural stability and mechanical properties after hydrogenation. On annealing, dissolution of the metastable β-Ti phase occurred. On hydrogenation, upto ~60 at.% hydrogen was obtained and hydrogen-induced amorphization occurred. The fracture strength of the hydrogenated composite indicated that it was mechanically stable even for high hydrogen contents.

Abstract: Effects of amounts of lignosulfonate and additives and reaction temperature on thermoplastics of lignosulfonate/polystyrene blends were investigated by rheometer through measurement of maximal torque, balanced torque and plasticized time. Optimum experimental parameters for preparation of lignosulfonate/polystyrene blends with excellent thermoplastic properties were obtained. The results of SEM and IR revealed that miscibility of lignosulfonate/polystyrene blends was improved, favorable for development of degradable lignosulfonate-based materials.

Abstract: After Industrial Revolution, energy has been recognized as an important factor which enhances the motive power for industry in the industrial society. However, recently the excessive consumption of energy pursuant to the rapid expansion of industry created serious problems of the exhaustion of fossil fuels as well as unusual change in the weather due to the mass discharge of carbon dioxide. We can say that after all proposals will boil down to the development of New & Renewable energy. The most suitable source of energy for this required change is solar energy. The advantages of solar energy are that it is renewable, infinite supplied and environmentally safe energy source, and the method of energy supply is in small scale and is decentralized. However, solar energy related products have the problems such as the limitation for installation, problems in maintenance and insufficient reliability, which have been the barrier to consumers to satisfy the purchase need for solar heat related products. In this research will perform thermodynamic analysis through the application of infrared ray thermal imaging camera and will discuss about the applicability of solar energy system and other fields as well.

Abstract: Line shaped electron beam was used for the recrystallization of nanocrystalline silicon layer that had been deposited on the low cost borosilicate glass-substrate in this paper. Polycrystalline silicon films of a 20μm thickness, which are the base for a solar cell absorber, have been investigated. Tungstendisilicide (WSi2) was formed at the tungsten/silicon interface as well as grain boundaries of the silicon. WSi2 improved the wetting and adhesion of the silicon melt. The surface morphology of the film was strongly influenced by the recrystallization energy density applied. Low energy density resulted in non wetted WSi2/W areas due to the reaction between the silicon melt and the tungsten. With the increased energy, the capping layer become smooth and continuous due to the pinholes becomes fewer and smaller. Excess of the energy density led to larger voids in the capping layer, more WSi2/Si eutectic crystallites, a thinner tungsten layer, and a thicker tungstendisilicide layer.