DETECTION OF SUBSTITUTIONAL ATOMS IN A GAMMA' PHASE BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

400 kV high-resolution electron microscopy is used to study the distri bution of foreign atoms which are present in substitution in a Ni3Al i ntermetallic compound. The presence of elements heavier than Al can be detected in the images. It is shown that these elements are located o n the Al sites. The contrast of atomic columns containing different el ements is analysed by multislice calculation and image simulation. The contrast analysis combined with a statistical approach leads to an es timation of the overall composition which is in agreement with previou s experimental results.