The Effect of Dislocation Substructure and Decomposition on the Course of Diffusionless Transformations

Abstract
The mechanical properties (yield strength, hardness, transformation stresses) and the transformation temperatures of SMA can be affected by the combination of different solid-state reactions. In this context the combination of local change in chemical composition by precipitation processes and the rearrangement of defects by recovery and recrystallization are of special interest. The influence of different heat treatments on Ni-rich β-NiTi-alloys was investigated by polarization light microscopy, TEM, DSC-measurements and microhardness tests above M_d. Of particular interest were the occurance and interactions due to the different nature of martensitic (M-) phase and R-phase transformation.