Katsura Kajihara

In situ SEM-EBSP observations of recrystallization texture formation in Al-3mass%Mg alloy

This study presents in situ observations of recrystallization texture formation in Al-3mass%Mg using SEM concurrent with electron back scattering pattern (EBSP) with hot stage. In the present discussion, the emphasis is on the characteristics of the preferred growth or the shrinkage of Cube and other oriented grains. The in-situ observations of recrystallization demonstrate clearly that the nucleation, growth and shrinkage of recrystallized grains occur simultaneously in each orientation in each region. The overall development of recrystallization texture depends on the balance of nucleation/growth and shrinkage/disappearance of each orientation during recrystallization. The preferential growth is determined by the grain boundary mobility between recrystallized grains or the clusters composed of several similar oriented grains, i.e. Cube clusters or S clusters, and neighboring deformed matrix, and the competitive growth with the surrounding grains. On the other hand, the isolated oriented grain and the strain-stored grains tend to shrink and disappear during recrystallization and grain growth.

In Situ EBSP Observations of Recrystallization in Commercial Purity Aluminum

This study presents in-situ EBSP observations of recrystallization in commercial purity aluminum sheets with different concentrations of solutes and different states of precipitation. The in-situ observations demonstrate clearly the behaviors of the nucleation and growth of recrystallized grains, and the movements of grain boundaries at an early stage of recrystallization. The high mobility of grain boundaries neighboring the deformed matrix was generally observed presumably due to strain-induced grain boundaries migration. The grain boundary motion was also found to strongly depend to the solute content level. These in-situ observations provide important evidence to show that the behaviors of grain boundary motion at an early stage of recrystallization leads to the grain size distribution and the curvature of grain boundaries after the primary recrystallization.

Development of Enriched Borated Aluminum Alloy for Basket Material of Cask for Spent Nuclear Fuel

New enriched borated aluminum alloys manufactured by melting process are developed, which resulted in supplying structural basket materials for spent nuclear fuel packagings. In this process, the borated aluminum alloys were melted in a vacuum induction furnace at elevated temperature than that of ordinary aluminum melting processes. Boron dissolves into the matrix at the temperature of 1273K or more, and fine aluminum diboride is precipitated and uniformly dispersed upon cooling rapidity. It is confirmed that boron is homogeneously dispersed with the fine particles of approximate 5µm in average size in the product. Tensile strength and creep property at elevated temperature in 1mass-%B 6061-T651 plate and 1mass-%B 3004 extruded rectangular pipe as structural materials are examined. It is confirmed that the both of borated aluminum alloys have stable strength and creep properties that are similar to those of ordinary aluminum alloys.Copyright

Effect of dispersoids on softening behavior in Cu-Fe-P alloys for lead frames

The effect of the amount of dispersoids on softening behavior and recrystallized microstructure of Cu-Fe-P alloy was examined by the extracted residue analysis method. The degrees of contribution of larger particles (larger than 1μm in an average diameter) and smaller ones (less than 0.1μm) to the softening behavior were considered in the quantitative aspect, respectively. It was found that the change of the order of 10-1mass% in the amounts of both particles has a great effect on softening behavior. The difference in the amount of fine particles changes recrystallized grain size distributions at similar hardness. In the specimen with a small amount of fine particles, coarse grains and wide distribution of grain size were observed after annealing. As a result, it was revealed that fine and homogeneous recrystallized microstructure was obtained due to just 0.35mass% of fine partcles, even if the amount of large particles increased.