Three-dimensional element concentration mapping of Al-Cu alloy was carried out using the K-edge subtraction imaging technique. Spatial inhomogeneity of copper concentration was evaluated using a solution heat-treated sample. The average value of copper concentration was 1.57% for the whole sample. From the observation of three-dimensional images, the copper concentration seems to be homogenized by the solution treatment. By evaluating several unit cubes of 20μm in one side, the variation of the copper concentration which varies between 1-2% was obtained. The three-dimensional concentration mapping revealed in more detail than before that homogenization by solution treatment at high temperatures for a long time appears to be insufficient. Furthermore, the influence of sample size was also evaluated by applying the K-edge subtraction imaging technique to materials with the same composition but different sample sizes.
