Influence of Training Cycles on Microstructure and Properties of NiTi Shape Memory Alloys

摘要

The influence of thermomechanical treatments on a binary near equiatomic NiTi shape memory alloy was studied with respect to mechanical and shape memory properties. The deformation behaviour both of martensite B19' at room temperature and high temperature phase B2 (parent phase) at 170 deg C was investigated by tensile tests. The range of near constant stress during deformation, the so-called martensite plateau, is more pronounced in the annealed samples. The yield strength of the high temperature phase strongly depends on the heat treatment condition. A two way shape memory effect could be induced by repeatedly heating and cooling under constrained conditions. Measurements of the transformation temperatures demonstrate a strong influence of the training procedure especially on the parent phase start and finish temperatures.