Multiply Twinned Phases and Microstructures in Ni-Al: A Transmission Electron Microscopy Study

Abstract

In today’s understanding of the behaviour of common as well as new materials the knowledge at the atomic scale of microstructures and phase transitions is crucial. One technique that provides information at this level and which is not averaged over bulk size objects is transmission electron microscopy (TEM). In the direct imaging mode contemporary instruments can provide lattice images of a wide range of materials which enables one to investigate the atomic structure of the matrix as well as single defects at or below the unit cell dimensions; this mode is usually referred to as high resolution electron microscopy (HREM). In the electron diffraction (ED) mode the full symmetry at any given region down to a few nanometers in size can be found. Moreover, phase transitions can be followed in situ under, e.g., temperature or stress gradient conditions in dedicated specimen holders. These features, together with the possibilities for local chemical analysis by energy dispersive X-ray (EDX) analysis or electron energy loss spectroscopy (EELS) make this experimental technique extremely valuable in the investigation of phase transitions and the involved microstructures and phases.