OBSERVATION OF CRYSTALLOGRAPHIC CONTRAST ON POLYCRYSTALLINE SPECIMENS BY MEANS OF CHANNELLING MICROGRAPHY TECHNIQUE

In order to reveal the crystallographic contrast from the surface of the polycrystalline specimen, two electron optical paths were analyzed. For the standard scanning path, the magnification of the channelling micrograph is controlled by the electron beam scanning angular field. The ratio between geometric and crystallographic contrast can be modulated by the signal processing method. For the defocused beam rocking path, the magnification is controlled by the defocused distance. The anomalous effects of the orientation contrast resulted by the deformed specimen may be interpreted by means of ECP superimposed on the channelling photograph.Observations were made of certain specimens such as W, Mo and 304 austenitic stainless steel. It seems that the present technique is available for study of both the orientation distribution and the deformation behaviour of the polycrystalline materials.