When Peter Hirsch produced the first images of defects or faults in crystalline structures using transmission electron microscopy at Cambridge University’s Cavendish Laboratory, he transformed our understanding of materials science and redefined our knowledge of crystallography.
In particular, in 1956 he and his team directly observed a specific type of fault, known as a dislocation, in pieces of stainless steel and aluminium foil, which previously had only been a somewhat controversial hypothesis. These faults are important because they control the ductility of the material, that is, its ability to sustain deformation before breaking.
