The constitutive equation in ambient temperature creep region of α-Ti was investigated by performing creep tests on solute-strengthened and/or cold-rolled titanium. Increasing solute content and/or thickness reduction decreases the steady state creep rate. The stress exponent increases with solute content, but it is independent of thickness reduction in low stress. Then, the microyielding stress, σ_my, is introduced to express the stress at which dislocations start moving. The stress exponent in ε̇_s− (σ−σ_my) graph becomes almost constant with the value of three even in the solute-strengthened and/or cold-rolled titanium. The constitutive equation for ambient temperature creep in α-titanium is proposed as ε̇_s=A (S) × (b/d) ^p× {(σ−σ_my) /E} ⁿ×exp (−Q/RT) , where n≃3, p≃1 and Q≃20 kJ/mol. The deformation mechanism map of titanium with ambient temperature creep region including microyielding stress is proposed.

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In order to impart metallic luster to AZ31 magnesium alloy, the conditions of surface treatment were optimized, and the formative mechanism of metallic luster on the surface was inferred from the results of surface analysis. The target of this study was the surface of AZ31 magnesium alloy that was polished by emery paper (#2000) . When the optimal acid aqueous solution treatment was applied, more than 60% of the magnesium in the film was oxidized. In addition, the thickness of the film was about 55 nm. It was confirmed that hydrogen generation was inhibited under the optimized surface treatment conditions. This optimization was performed by examining oxidant addition and the temperature of the acid aqueous solution, and metallic luster was successfully imparted to the alloy. In the optimal acid aqueous solution treatment, it was found that the reaction rate of magnesium oxide formation was faster than that of the dissolution of magnesium from the film composed of magnesium oxide on the surface. For surface treatment conditions in which a dull surface was obtained, it is speculated that the surface became rough due to the generation of hydrogen.

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Recrystallization behaviors in an Al–Mg–Si alloy have been intermittently observed by means of SEM-EBSD in detail. A specimen of Al–0.73 Mg–0.38 Si–0.26 Cr (mass%) alloy was cold-rolled with reduction rate of 30%, then annealed at 673 K. Annealing, ion-polishing and EBSD measurement were repeated and changes in microstructures were observed on the same area in the specimen during annealing up to 4.8 ks. At the early stage of annealing, crystallites (subgrains) formed near grain boundaries, and they grew into recrystallized grains without changing their orientations. The orientation of the crystallite is in the range of lattice rotation due to cold-rolling. Prior grains in which {100} planes were parallel to the specimen surface tend to form crystallites with {100} and {110} orientations. While prior grains with {110} orientation tend to form {100} oriented crystallites. Crystallite invaded neighboring prior grains with the strain induced boundary migration mechanism. The invaded grain was separated from the mother grain by other invading grains. Grain boundary migration and mutual intersection resulted in formation of recrystallized grains surrounded by large angle grain boundary in the neighboring prior grain. Orientations of the prior grains are maintained in the recrystallized grains with changing in the range of lattice rotation.

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It was found that coupons of aluminum can material 5182 were corroded in dehydrated methanol with aluminum chloride. The higher solution temperature was, the more rapidly dissolution occurred. It is shown that similar pattern of XRD analysis, particle size distribution analysis and particle morphology observation revealed that corrosion product of 5182 coincided with aluminumtrimethoxide supplied in commercial market when they were hydrolyzed and then calcinated. The 5182 dissolution product was electrochemically interpreted as corrosion product which is aluminumtrimethoxide oxidized in methanol containing aluminum chloride as catalyst.

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