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In order to investigate the effect of boron on the precipitation behavior of β phase in Al-Mn-Mg-B alloy used as a material for cask baskets, 1.00 © 104 hours aging treatment was carried out focusing on the temperature history in the cask as in the previous report, and the Timetemperature-precipitation diagram and Supersaturation-diffusion length-precipitation diagram were evaluated using the change tendency of the specific resistance obtained. In the Al-Mn-Mg-B alloy, although grain refinement by AlB2 was confirmed, the effect of boron addition on the precipitation rate of β phase was hardly recognized. That is to say, it was confirmed that the grain boundary and the interface between B compounds and matrix phase hardly contributed as nucleation sites of β phase. In conclusion, it is considered that the reduction of the solid solution Mg content in the Al-Mn-Mg-B alloy does not occur even after 60 years if the Mg content is 1.0 mass% as in the Al-Mn-Mg alloy. [ABSTRACT FROM AUTHOR]

Al-Mn-Mg alloys have been considered as the most suitable basket material of transport and storage casks for spent nuclear fuels. However, the Mg content should be defined with consideration of their prospective heat histories; e.g. exponentially decreasing in temperature from about 200°C to 100°C during the fuel storage up to 60 years. In this research, precipitation behavior of ¢ phase (Al3Mg2) in AlMnMg alloys was analyzed at various temperatures, focusing on the effects of the amount of Mg. Time-temperature-precipitation (TTP) diagrams for these alloys were depicted by a model which had been developed based on classical nucleation theory. The TTP diagrams were further rebuilt to "degree of supersaturation-diffusion length-precipitation (SLP) diagram", where the degree of supersaturation (S) and diffusion length multiplied by cubic root of Mg concentration (L+A) were involved for predicting the starting condition of precipitation. From the SLP diagram, Mg content of 1.0 mass% was found to be able to maintain sufficiently the solid solution strengthening for 60 years. [ABSTRACT FROM AUTHOR]

In this study, we examined the distribution of nanostructures in the interdiffusion layer of AlMg/AlZn/AlMg multilayer composites with different layer width via microbeam small-angle X-ray scattering (SAXS) measurements and direct observation using transmission electron microscopy (TEM). The changes in scattering profiles across the graded interfacial layers reflected the spatial change in the volume fraction, average size of precipitates, and their distribution in the sample. Microstructural parameters obtained from the SAXS analysis were used to explain the local hardness change in the interface area. Within the single interdiffusion layer of AlZnMg alloy, both of the Orowan and cutthrough mechanisms were observed. TEM imaging was used with the same projection of SAXS to analyze the various shapes of the precipitates to explain the anisotropy in the 2-dimensional scattered intensity measured via SAXS. The present results revealed the spatial distribution of nanostructures with averaged parameters and explained the local mechanical properties within the interface region of the multilayer composite sheets. [ABSTRACT FROM AUTHOR]

The effect of precipitates on filiform corrosion (FFC) growth of coated Al-Mg-Si-Cu alloys with different coolings and chemical components was investigated using a cyclic corrosion test and dynamic polarization in an acid solution. Total FFC growth was accelerated by air cooling, while being suppressed by water quenching for high Cu containing Al alloy. Comparison of water quenching with air cooling showed that the cathodic current densities and number of precipitates including Cu were lower after water quenching at high Cu containing Al alloy. These results suggest that suppression of precipitates including Cu improves the FFC growth resistance of Al-Mg-Si-Cu alloys. [ABSTRACT FROM AUTHOR]