TWSME in Cu-Al-Ni Alloys Obtained by Stabilised Stress Induced Martensite

Abstract
The effect of deformation degree, temperature and time of ageing on the TWSME has been studied in polycrystalline and single-crystalline Cu-Al-Ni alloys. The results confirm that to obtain the best TWSME one needs to select the training parameters. The trained single crystals exhibit a lower TWSME than the polycrystalline alloys for the same training conditions. In the trained single crystals a single martensite variant has not been observed, but they showed a fewer variants than the untrained samples. The TEM studies of the trained samples exhibit a complex dislocation arrangements which interact with very thin induced plates of martensite. Ageing of the one of polycrystalline alloys caused precipitation of coherent γ₂-phase particles. No precipitates were found in the second one and in the similarly trained single crystals although in these alloys a significant TWSME was observed. This means that the role of the γ₂-phase particles presence to obtain the TWSME by ageing under stress is not that important as it has been suggested.