The solution-based electrochemical process has long been widely used in various fields, such as electroplating metals, metal oxides, and compound layers in mechanical, anti-corrosion, electrical, electronics and energy applications. This process encompass oxidation-reduction reactions, acid-base reactions, and ligand-exchanging reactions relating to the equilibrium potential, solution pH, and stability constant. Here, techniques used in various calculations for the equilibrium potential, pH, soluble species ratio, potential-pH diagram, and solubility curves were described based on thermodynamics, including the chemical potentials of chemical substances and the stability constants of metal complexes. The practical aspects of these calculations were discussed in the electrochemical and chemical preparations of metal compound precursors, metal oxide and hydroxide layers, and the CuO/Cu₂O bi-layers for solar cells and photocathode applications.

A hot extruded AZ80-F magnesium alloy was multi-directionally forged (MDFed) up to a cumulative strain of ΣΔε = 2.4 at warm temperatures of 543 K, 573 K and 593 K. Fine grained structures were gradually developed with increasing cumulative strain due to extensive occurrence of dynamic recrystallization. Bimodal grain size distribution tended to appear when MDFed to lower cumulative strain and/or at lower temperatures. The yield stress of the MDFed AZ80-F alloys with homogeneous grain size distribution followed the Hall-Petch relationship. MDFing to ΣΔε = 2.4 at 543 K exhibited the most excellent balance of mechanical properties of 260 MPa yield stress, 347 MPa tensile strength and 24％ elongation to fracture. The warm MDFed Mg alloys accepted additional 10％ cold rolling to cause further strengthening by strain hardening and sharp basal texture evolution.

Titanium alloys have been used not only in air frames for commercial aircrafts, but also in its jet engine components such as fans and compressor disks, which have a function at relatively low temperatures up to 673 K. Near β-type Ti-5Al-2Sn-2Zr-4Cr-4Mo (Ti-17) exhibits greater strength, crack propagation resistance, and creep resistance at intermediate temperatures compared with those of α+β-type Ti-6Al-4V. In particular, it is important to estimate the fatigue life of engine components made of Ti-17. To solve this problem, the quantitative relationship between fatigue properties and microstructural factors of Ti-17, therefore, in this study, the fatigue properties including tensile properties and microstructures of Ti-17 samples fabricated by hot-forging hot-forged at various temperatures followed by high and low temperature solution treatment (ST) and same aging treatment were investigated to define the quantitative relationship between the fatigue properties and the microstructural factors.

The microstructures of all forged Ti-17 samples exhibit elongated prior β grains composed of two different microstructural feature regions: mainly acicular α and fine equiaxed α phase regions. The volume fraction of acicular α regions decreases with in the increasing ST temperature. The Vickers hardness, 0.2％ proof stress and tensile strength increases with increasing ST temperature. On the other hand, the elongation and reduction of area exhibit a reverse trend to that of Vickers hardness, 0.2％ proof stress and tensile strength. The Ti-17 samples forged at 1173 K followed by solution treatment at 1073 K and aging treatment exhibits the highest fatigue limit of 975 MPa. The fatigue strength of the forged Ti-17 samples is considered to be strongly related with the microstructural factor such as the volume fraction of the equiaxed α phase region, which is one of crack initiation sites in the forged Ti-17 samples subjected to ST at low temperature and aging, and the difference in strength between the acicular α phase and the fine α+β phase region, which leads to the crack initiation in the forged Ti-17 sample subjected to ST at high temperature and aging.

Ultrafine-grained Al-Mg-Sc alloys were fabricated by the multi-directional forging (MDF) with different number of forging passes of 3, 9 and 15, i.e., to cumulative strains of ΣΔε = 1.2, 3.6 and 6.0, at room temperature. The achieved average grain sizes were 950 nm, 680 nm and 360 nm at 3 passes, 9 passes and 15 passes, respectively. Peak-aging treatments at 473 K for 172.8 ks were adopted for a portion of specimens after MDF in order to obtain finely dispersed Al₃Sc precipitates. Grain coarsening did not take place in all the specimens during the aging. The activation volume for plastic deformation was estimated from the strain-rate jump tensile tests before and after the aging. Aging-free 3-pass and 9-pass specimens showed positive temperature dependence of the activation volume, while that of the aging-free 15-pass one bearing the smallest grain size exhibited a negative temperature dependence. Contrary to these results, values of the activation volume in the peak-aged specimens were approximately identical regardless of grain size or deformation temperature. These results strongly suggested that, due to the precipitation of Al₃Sc, the rate-controlling process of deformation was changed from interaction between forest dislocations and mobile dislocations for the aging-free 3-pass and 9-pass specimens to interaction between mobile dislocations and Al₃Sc precipitates, or from bowing-out of dislocations from grain boundaries for the aging-free 15-pass specimen to the interaction between the mobile dislocations and precipitates.