The Effect of Thermal Cycling on B2→B19→B19′ Transformations of Ti<SUB>50</SUB>Ni<SUB>40</SUB>Cu<SUB>10</SUB> Shape Memory Alloy by Dynamic Mechanical Analyzer

Abstract

The effect of thermal cycling on B2→B19→B19' transformations of cold-rolled and annealed Ti 50 Ni 40 Cu 10 SMA was examined by DMA. Experimental results point out the transformation peak temperature and its tan δ peak value of B19→B19' transformation are more suppressed by thermal cycling than those of B2→B19. This is because of the different microstructures between B19 and B19' martensites in which B 19 is a defect-free martensite but B 19' has plenty of twinning. Dislocations induced by thermal cycling can hinder the mobility of twin boundaries of B19' martensite and cause different thermal cycling effects on B2→B19 and B19→B19' transformations. Thermal cycling also shows an obvious effect on storage modulus E 0 values of B 19 and B 19' martensites and their E 0 values increase with increasing thermal cycles.