Magnesium alloys have very poor plasticity at room temperature due to their crystal structure, i.e. hexagonal close-packed structure. Therefore, these alloys are usually deformed at high temperatures because the numbers of active slip planes increase and bring on the dynamic recrystallization. Although it is necessary for optimizing the processing conditions to understand a recrystallization behavior during the deformation, it is still unknown. That comes from the difficulty to observe the change of microstructures in one particular grain and the neighborhood of the grain. In this study, we tried to observe the microstructure evolution during deformation at room and high temperatures using an Electron Backscatter Diffraction (EBSD) apparatus with newly developed specimen stage for in-situ observation. As a result, we succeed to clearly observe the tensile twining at the fixed position during the deformation at room temperature. Furthermore, we can see grain boundary sliding and the grain growth during the deformation at high temperature of 473 K.

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The effects of the micro groove arrays formed on the tool surface, and the viscosity of lubricant, on surface quality of aluminum products were investigated, by carrying out plane strain extrusion experiments. Eight different plane plate tools were prepared for the experiments. One, a flat plane tool without the groove arrays. The other seven were tools with surfaces having micro groove arrays. Those seven tools include, two with the vertical cross sectional profiles of the grooves, two with the depth distributions of the groove arrays and three with locations of the groove arrays on the tool surface. The workpieces (billets) are annealed aluminum, A1050 (JIS) , and four paraffinic mineral oils of different viscosity were used as lubricants in the experiments. It was found that the vertical cross sectional profiles and depth distribution of the groove arrays affect the initial extrusion process, and that application of a tool with groove arrays is useful in the extrusion process for obtaining a good surface finished product using a wide viscosity range of lubricants.

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The effects of Zn addition to the filler, Cu addition to the core and the filler thickness on the corrosion resistance of the brazing sheet were investigated with SWAAT. In case of the brazing sheets containing Zn in the filler or Cu in the core, the corrosion depth was decreased and the perforation period was increased with increasing the filler thickness. In case of those brazing sheets, the corrosion potential of the surface layer was less noble than that of the core, and the corrosion potential difference between the surface and the core was increased with increasing the filler thickness. According to the galvanic coupling immersion test, the corrosion potential difference between the surface and the core was required more than 10 mV in order to have the sacrificial anode effect of the surface. The thickness of the sacrificial anode layer, defined as the layer whose corrosion potential was less noble than that of the core for 10 mV or more, was increased with increasing the filler thickness. The perforation period in SWAAT was increased with increasing the corrosion potential difference and the thickness of the sacrificial anode layer.

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Effects of Fe content on corrosion resistance in fluoride surface layers formed on specimens of a magnesium alloy, AZ31B, have been investigated in detail. The specimen was dipped into molten NaBF₄ at 693 K for 10.8 ks to form fluoride layer. Crucibles made with a mild steel and with an alumina were used to prepare the molten NaBF₄. Corrosion resistance was evaluated by in-situ observations using a laser microscope with dipping the specimen into a 0.02 N HCl solution, and also by an immersion test using a 5% NaCl solution at 308 K for 259.2 ks. Weight loss after the salt immersion tests showed that corrosion resistance of the specimen fluoride treatment in the alumina crucible was superior to that of the specimen treated in the steel crucible. The fluoride layer of the specimen prepared with using the steel crucible was contaminated with Fe, which was shown by SEM-EDX analysis. Significant corrosion was not observed after the salt immersion test on the specimen fluoride-treated in the alumina crucible, even on the cross-cut specimen.

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The compressive torsion process (CTP) is applied for consolidation of aluminum machined chip wastes to investigate a possibility of a new solid state recycling for aluminum alloy. The machined chips were consolidated by the CTP under the different temperatures and rotation times, and then the microstructure and tensile properties were investigated. It was possible to consolidate aluminum chips sufficiently into a cylindrical specimen by the CTP even at room temperature. The tensile strength of the specimen processed by the CTP was higher than that of annealed alloy made from an ingot metallurgy process. The tensile strength increased as the processing temperature decreased. The enough elongation over 15% was also obtained all over the specimen processed at room and elevated temperatures. It was concluded that the CTP had the availability of a new solid state recycling process with upgrading of aluminum alloy.

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It was found that aluminum alkoxide reaction of aluminum alloy 6063 occurs in ethyl alcohol containing aluminum chloride. The reaction is explained by the superimposition of Al/Al³⁺ reaction as the anodic reaction and ethanol/ethylate reaction as the cathodic reaction. In an environment containing chloride ions, an Al/AlCl₃ reaction participates in anodic reaction above and then becomes dominant anodic reaction. Rate of aluminum dissolution by the Al/AlCl₃ anodic reaction in ethyl alcohol is accelerated due to the fast system which has low polarization resistance. It is shown that aluminum alkoxide (aluminumtriethoxide) as corrosion product will produce hydrogen peroxide on the way of chain process of productions of ethyl chloride, diethyether and ethylether peroxide. It is also pointed out that the hydrogen peroxide will play a strong cathodic role in further pitting corrosion process.

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