The phase transition hysteresis and bidirectional memory effect of the TiNiCu coil spring designed in the first phase of the Metal World are studied and analyzed to find the best heat treatment system in order to obtain a good performance bidirectional memory alloy spring to achieve the driving performance. Experimental Methods Materials used in the experimental materials were Ti-43 at% Ni-5 at% Cu alloy wires of φ 0.50 mm.
The shape memory alloy wire was wound around a cylindrical mold with a pitch of 0.1 mm, a spring diameter of 4.5 mm, and an effective number of turns of 10 turns. Training of the spring at different heat treatment temperatures TiNiCu coil springs were subjected to a constrained heat treatment at 400 ° C, 450 ° C, 500 ° C × 1 h, and air cooled to room temperature. The two-way memory effect is trained on the spring after processing. The training process (shown in Figure 1) is: the training process of the bidirectional memory effect spring (1) at room temperature (the spring is in the martensite state). After stretching to a pitch of 12 mm, the spring will elongate due to elastic deformation after the external force is removed.
(2) The tensioned spring is placed in boiling water, and the TiNiCu alloy undergoes an inverse martensitic transformation, and the spring contracts.
(3) Put the spring back into the room temperature water, and the spring returns to the shape processing state.
TiNiCu coil springs heat treated at different temperatures were trained several times to study the change of shape recovery rate with the number of training times.
After the shaping treatment, the TiNiCu coil springs were subjected to a 500 ° C × 1 h setting process for training of different phase springs, and air-cooled to room temperature. In order to determine the phase transition temperature of the spring, the above-mentioned heat-treated spring was subjected to DSC test on a Seiko Exstar 6000 differential scanning calorimeter, and the rate of heating and cooling was 10 ° C / min. Then the spring was subjected to different temperatures (25 ° C, 72 ° C). , 98 ° C) thermomechanical training.
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