Structural studies of shape memory alloys by means of hrem

摘要

The paper reviews some applications of the High Resolution Electron Microscopy (HREM) technique to the study of particular structural and microstructural features of the shape memory alloys. These alloys present unusual thermomechanical properties, like the shape memory effect and pseudoelasticity, which are related to a thermoelastic martensitic transformation. Several topics are treated, like the intervariant boundary structure of 18R martensite in Cu-based alloys, the substructure of this phase, the twin-boundary structures in Ni-Ti martensites, the structure refinement of Ni_2Al precipitates in Ni-Al alloys, the gamma -phase precipitates in Cu-Zn-Al alloys and the premartensitic effects in Ni-Al and Ni-Mn-Ga alloys. At the end, a new method for HREM image processing, based on the phase of the Fourier transform, is commented.