Study On The Shape Memory Effect And Property Of Fe-Mn-Si-based Alloy

The shape memory alloy is a new kind of functional materials and has been focused in recent decades. The main characteristic of this material is the shape memory effect. Compared with others alloys, Fe-based shape memory alloys have such advantages as high intensity, better plasticity, simple preparation technology, low cost, convenient application and so on. So they become the focus of recent research.Fe-30Mn-5Si and Fe-20Mn-5Si-5Cr-3Ni alloys of different composition were made in this paper. Microstructures of the alloys were observed and studied by means of optical microscope, SEM , XRD and so on. The influence of annealing temperature, prestrain treatment, thermal-mechanical processing and quenching processing on shape memory effect has been investigated. Corrosion resistance of the alloy has also been studied. Then the alloy of better property was used to make clinch and the application of Fe-based shape memory alloys would be promoted.The transformation of fcc austenite to hcp martensite takes place in Fe-30Mn-5Si Fe-20Mn-5Si-5Cr-3Ni alloys when they are applied to external stress. The reverse transformation of martensite to austenite takes place when the alloys are annealed after the external stress is unloaded. The mechanism of martensite transformation is based on stack fault nucleation system and induced by the moving of Shockley imperfect dislocations. The new formed structural system made up of two Shockley imperfect dislocations and a piece of fault cannot slide easily because of low fault energy. So the way of reverse transformation is determined exclusively.It was found that percentage recovery decreases with the increasing of prestrain and increases with the increasing of annealing temperature and there is a higher percentage recovery when up to 600℃...