The thesis will be focused on analysis of deformation mechanisms in shape memory alloys by thermomechanical testing and transmission electron microscopy. Functional thermomechanical behavior of NiTi is due to deformation processes derived from martensitic phase transformation which are ideally reversible – i.e. these processes do not leave any lattice defects in the material exposed to closed thermomechanical cycle acreoss the transformation interval. Unfortunately, this is not exactly true in real material, particularly if the martensitic transformation proceeds under external stress, incremental plastic deformation occurs and lattice defects are left in the austenite phase. The scope of the dissertation will be to perform dedicated thermomechanical loading tests on thin NiTi wires and to observe and analyze the left lattice defects by scanning and transmission electron microscopy with the aim to reveal the cause of the cyclic instability and functional fatigue of NiTi.
Investigation of deformation mechanisms in shape memory alloys by thermomechanical testing and transmission electron microscopy
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