Two-Way Shape Memory Effect Induced by Bending Deformation in Ductile Cu-Al-Mn Alloys

Martensitic transformation temperatures and the two-way shape memory effect (TWME) in ductile Cu-Al-Mn alloys deformed at room temperature were investigated using differential scanning calorimetry (DSC) and the bending test. The M s and A f temperatures were found to increase slightly with increasing degree of pre-deformation, while the M f and A s temperatures decreased. The TWME is strongly influenced by the M s temperature and the grain size of the specimens, i.e., the highest degree of TWME is always obtained in the specimens with M s -100°C and the TWME increases with increasing ratio of grain size to specimen width, where the maximum value of TWME = 3.2% was obtained in the present study. In situ observation of the surface relief at several temperatures on the deformed specimens was also performed and it was found that some restricted martensite variants grow and shrink with temperature change without the typical self-accommodation microstructure in the specimens with large TWME.