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The shape memory effect in systems Cu-based alloys

Jo?ica Bezjak A. Professor

Till now, the shape memory effect has been found in Cu, Ni, Au, Ag, Nb and Fe-based alloys. Among them, the largest practical usability have Cu and Ni-based alloys but latter have better mechanical properties (higher hardness, better deformability, as well as temperature and corrosive resistance). Two new chemical compositions of Cu-Zn-Al based alloys were selected in order to analyse their phase transformation and shape memory behaviour. Both chemical compositions of alloys are relative closed to each other and selected in such a manner that their temperatures of martensite transformation Ms would have been above room temperature. The influence of deformation and heat treatment was analysed for both alloys. Temperature of martensite transformation can be measured with different methods. X-ray method and electrical resistivity measurement at elevated temperatures are cited the most frequently in the literature. In the present work, dilatometry (DIL) was used as a new method for a detection of martensite transformation down to –100°C. Transmission electron (TEM) and light microscope with heated table (HT/LM) were used in order to explain and to confirm temperatures of martensite start (Ms), martensite finish (Mf), austenite start (As) and austenite finish (Af) determined by DIL.