Abstract
The two way shape memory effect (TWSME) is not the inherent material property, but after application of suitable thermomechanical treatment (training) the high reliability and durability of this effect can be obtained. The study of the TWSME is realised with the TiNi alloy (50.4 at.% Ni) by use of the special specimen form (C-form, diameter of wire is 2.5 mm) for three training variations. The investigated alloy has martensite structure in initial state at room temperature (96% of B19'). The evaluation of TWSME includes the heating of specimens, placed into apparatus containing two springs, at 85 °C (B2 structure) and the cooling to room temperature. After the applied thermomechanical treatment the stable durability of the TWSME up to 10000 loading cycles is achieved. Further, the substructural analysis of investigated specimens after the training cycles and the TWSME is made. The physical metallurgy analysis of the studied effect is based on the formation of special dislocation arrangement in the course of the training cycles, leading to the uniform preferential orientation of the martensitic plates.

Key words
shape memory effect (TWSME), thermomechanical treatment, training, TiNi alloys, martensite structure

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