Effects of two kinds of electroless Ni-P plating and a baking treatment after plating on the temperature-dependent hydrogen desorption behavior, tensile properties, and fatigue properties of 6061-T6 aluminum alloys were investigated, and the results were discussed. Thermal desorption analysis (TDA) revealed that each plating causes hydrogen absorption into the substrate, which was found to reduce the mechanical properties. After plating, the baking treatment significantly reduced the hydrogen amount in the substrate and improved the mechanical properties. The fatigue strength of the low-phosphorus type plated specimen was increased to 160 MPa by the baking treatment, and a fatigue ratio of over 50% was obtained.

Based on the hydrogen-vacancy cluster theory, the reduction in fatigue strength of high-phosphorus type plated substrate is assumed to be caused by the formation of hydrogen-induced vacancies due to hydrogen incorporated into the substrate by plating, which migrate and form nanovoids during fatigue testing.

In this study, adsorption behavior of oxygen on platinum surface in Pt/C-based catalysts used for oxygen reduction was investigated in terms of the surface plane and lattice distortion of platinum by a first-principles calculation. The calculations revealed that Pt(110) surface has higher oxygen adsorption stability than Pt(111) surface. Dissociative adsorption of the oxygen molecule was observed only in the model with a distortion of about -4% on the Pt(111) surface, whereas such reaction was observed on many Pt(110) surface even with and without distortions. In other words, both surface distortion and surface plane would play important roles for the oxygen adsorption behavior of ORR, suggesting that the Pt/C-based catalysts prepared with a large amount of Pt(110) surface with distortions exposed are more likely to proceed through a pathway involving dissociative adsorption of molecular oxygen.

The causes of the differences of the graphite nodularity (ratio of graphite spheroidization) depending on the methods built on the Japanese Industrial Standards (JIS) in spheroidal graphite cast iron castings were investigated based on the factors influencing the roundness (roundness factor or roundness shape factor) and area (cross-sectional microstructure) of the graphite particles on the cross-sectional microstructure and the graphite nodularity. Although the effects of the sharpness and resolution of the image data and the binarization threshold in the image analysis on the roundness and the area of the mock graphite particles were generally small, the roundness of the hexagram or octagram increased beyond 0.6 with a decrease in the sharpness of the resolution. Meanwhile, the relationships between the graphite nodularity by JIS and ISO methods built on the JIS for various combinations of the roundness and area showed that the nodularity by the ISO method is often greater than that by the JIS method. This is because the graphite nodularity by the ISO method depends on whether the roundness is less than 0.6 or not. These suggest that the smaller graphite nodularity by the JIS method than that by the ISO method can be caused by many unsharp graphite particles, many small out-of-round particles in the low-resolution image, and/or by the manufacturing condition targeting the roundness of a little over 0.6.