50 years of TEM of dislocations: Past, present and future

A historical review of the study of dislocations by the transmission electron microscopy (TEM) in the last 50 years is presented. TEM has become a indispensable technique for materials scientists since the first observations of dislocations by this technique was reported in 1956. The year 1969 saw the development of the methods for simulating images of dislocations inclined in the foil, based on the Howie-Whelan equations. Other major advances included the development of many heating, cooling, straining and environmental cell stages, simulated by the arrival of microscopes in the 1970s, which were developed to improve resolution and penetration. Microscopes became to be available in the 1970s, in which electrons could be focused into small probes on he specimens, and which combined imaging, diffraction, and X-ray analysis. Another important advance in instrumentation is the development of energy filters, which enables images to be obtained that have suffered a particular energy loss.