dependence of interdiffusion coefficients (D) on the concentration of Al. From the values of coefficients the activation energies for interdiffusion (Q) were obtained as the function of Al concentration in the alloy. D at each temperature was strongly upon temperature in the Arrhenius plot showed a good linearity, from which the activation energy for interdiffusion was calculated. The energy decreased steeply with Al concentration down to 43kcal/mol in a disorder range and increased in an ordered range in general. But the activation energy showed a high value (69kcal/mol) at the initial stage of the ordered phase. Fine alumina markers placed initially on the test piece were found in the ordered phase after annealing at each temperature to shift to higher Al concentration with increasing temperature and the intrinsic diffusion coefficient of Al was about 1.4 to 2.0 times higher than that of Fe. The mean activation energies in the range of composition of 30.5 to 42.8 at% Al of both constituents were about the same (60kcal/mol).
Neutron imaging using a pulsed neutron time-of-flight method can give an energy
dependent transmission image, namely, spectroscopic image. This image includes the structure
information if the sample is coherent scatterer. Here, two examples are introduced. First, we
obtained the transmission image of a welded sample of SS304 and 308. Change of the crystal
structure depending on the position was observed. Furthermore, we measured spatial dependent
transmission of SS samples treated in different ways, surface treatment and whole body treatment.
There were almost no spatial dependent change, but the cross section change was found between
surface and whole body treatment samples. It was suggested that this might be due to the
difference of a grain size. These results demonstrated that the spectroscopic imaging using a
pulsed neutron source is a useful tool for material characterization.
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