Shouichi Ochiai

Influence of the Cube-Texture and the Grain Growth on the Creep Behavior in Platinum-10%Rhodium Alloy

In Pt-10mass%Rh alloys which were recrystallized using full annealing at or above 1273K after the cold rolling with the reduction ratio of both 90% and 98%, the formation of cube texture has already been found. When these primary recrystallized alloys are subjected to the further annealing at higher temperatures, the occurrence of the secondary recrystallization can be expected. In this study, the development of the cube texture and the process in the coarsening of crystal grains during the secondary recrystallization were investigated. In addition, the creep tests were carried out for the secondary recrystallized alloys and resultant creep properties were compared with those for the primary recrystallized alloys. It became clear that the cube texture which further developed during the secondary recrystallization in 98% rolled specimens exhibits the greater thermal stability than that in secondary recrystallized 90% rolled ones. During the secondary recrystallization, it was confirmed that the grains coarsened according to the law of tm, where t and m show time and a constant, respectively. The higher development of the cube texture and the coarsening of grains during the secondary recrystallization were found to have remarkable effects of improving the creep resistance.

Sharpening of Cube Texture during Grain Growth in High Purity Aluminum

Grain growth in cube-textured aluminum was investigated by transmission Laue photographs obtained at the same point in specimens with progressing annealing at the heating rate of 20 deg/h. High purity aluminum for electrolytic capacitor was cold rolled to 98 % reduction, and subsequently partially annealed at 230 °C for 6 h and rolled 22 % reduction. On the light rolling, asterisms toward RD were observed near by direct beam, suggesting that lattice rotation around TD was caused in cube grains by light rolling. After annealing to 300 deg, fine Laue spots were detected in the asterisms. Those fine spots were indexed as 100 spots due to diffraction in {100} nearly parallel to the ND-TD plane. After disappearance of Debye arcs due to diffraction in untransformed matrix, cube texture was observed with orientational spread around TD. With continuing annealing to 540 °C , grain growth occurred at the expense of cube grains whose orientations deviated from the exact cube orientation around TD , resulting in sharp cube texture formation.

Mechanical and Fatigue Properties of the SiCp/Al Composites

Mechanical and fatigue properties of the SiCp/Al with three different SiC particle volume fractions: 5%, 7.5% and 10% as well as Al6061 alloy were examined with tensile test, hardness measurement and fatigue crack propagation test. Tensile strengths and hardness of the SiCp/Al increased together with SiC particle volume fraction. It was checked that tensile strengths of the SiCp/Al had a certain relation with the corresponding hardness. On the other hand, fatigue crack propagation behavior (FCPB) of the SiCp/Al was faster than that of the AA6061. Besides, difference of the FCPB among SiC particle volume fractions was not pronounced. However, The FCPB slightly increased together with SiC particle volume fraction. It was noted that fatigue properties of the SiCp/Al was more affected by local volume fraction in front of crack tip than bulk volume fraction. In addition, the presence of SiC particles delayed fatigue crack initiation effectively because the percentage of fatigue crack initiation life to the whole fatigue life was a maximum of 38%, larger than that of ordinary structural materials.

Mechanical Properties and Oxidation Behavior of TiB2 Particle Dispersion Strengthened TiAl Intermetallic Compounds

Publisher Summary Compacts with the addition of TiB2 particles were consisting of TiA1, Ti3Al and TiB2 phases. The strength of compacts increased with increase of vol% of TiB2. This fact indicates the obvious dispersion strengthening effect of TiB2for TiA1 intermetallic alloy. The strain rate sensitivity exponents were found to be larger than 0.3 at 1373K for any specimen, suggesting the development of superplasticity. Although mass gains during oxidation test of the matrix and 10TiB2 alloys were very small of less than 10 g/m 2, large one of 80g/m 2 was measured for 20TiB2 alloys. It was observed that the oxidation scale near the surface consisted of alumina layer and the volume of TiO2 scale increased with increasing TiB2 volume.