Electron Transmission Through Thin Metal Sections with Application to Self-Recovery in Cold Worked Aluminum

D I R E C T experimental evidence for the wave nature of the electron first demonstrated by Davisson and Germer was based on a property unique to wave phenomena; namely, interference or diffraction. The ability of a regular or periodic array of atoms to diffract electrons (just as a ruled grating diffracts light) has led to the construction of quite general theories of the behavior of matter, the band theory of solids being a notable example. The forbidden energy zones in a crystal are simply a result of diffraction of the valence electrons by the periodic structure. On the other hand, the results of straight forward diffraction experiments are a consequence of the zone or band structure of the crystal thus illustrating an interesting closure or completion of the cycle. This paper is concerned with the interpretation of electron interference phenomena occurring in thin metal sections particularly as it pertains to structural changes accompanying plastic deformation. Diffraction effects are observed not only in the usual electron diffraction methods but in electron microscope images as well. The chief difference is that in the former the diffracted rays are of primary interest while in the latter the regions of the crystal in which diffraction occurs are imaged with the diffracted beams removed by the objective aperture. Electron microscope images of crystalline materials thus offer a high resolution method of studying variations in diffracting power. This information can then be interpreted in terms of structural features.