Measurement of Local Textures With Transmission and Scanning Electron Microscopes
Transmission and scanning electron microscopy methods are discussed for the determination of grain orientations. For the study of local textures with a TEM electron-transparent thin samples are required. The standard techniques of orientation determination grain by grain are the interpretation of selected area electron spot and microbeam Kikuchi diffraction patterns. Specimen areas smaller than 500 nm or 50 nm in diameter can be selected. More recently selected area pole-figures can be measured directly with a TEM technique similar to the conventional transmission X-ray method.The orientation of grains in a bulk sample can be obtained with a scanning electron microscope from reflection Kikuchi (i.e. electron backscattering) and channeling patterns. Local resolution is approximately 1 μm or 5 μm, respectively.Since the interpretation of electron diffraction patterns is tedious, techniques have been developed to perform measurements on-line by interfacing the electron microscope to a computer. An outstanding advantage of texture measurements by electron diffraction is the high local resolution and the ability of imaging the microstructure of the sampled region. Experimental results of individual grain-orientation measurements may be represented statistically by inverse pole-figures, orientation distribution functions and misorientation distribution functions.