TEM study on the microstructure of Cu–Al–Ag shape memory alloys

In the last few years, a new Cu–Al–Ag shape memory alloy with high transformation temperature (Ms above 250 °C) has been developed. In order to investigate the influence of Ag content on the shape memory effect, four Cu–Al–Ag alloys with similar Al contents, but different Ag contents were selected. The microstructure and the transformation stability during thermal cycles of the four alloys have been studied by means of transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). It was found that with the decrease of the silver content from 2.78 to 0.32 wt.%, the microstructure of the martensite changed from dislocation tangles to parallel dislocation lines and to partial dislocations; and that with the decrease of the silver content, the stability of the phase transformations increased. The influence on shape memory effect is also discussed.