Study On Phase Transition Of NiMnInFe Alloy Under The Condition Of Magnetic Field By Synchronous High Energy X-ray

The NiMnInFe magnetically controlled shape memory alloy is the most ideal new smart material after the NiMnGa alloy. It has the advantages of shape memory effect, rapid response frequency, precise controllability, maximum stress and high reversible strain output. Because the martensitic transformation of NiMnInFe alloy is directly induction by magnetic field, the NiMnInFe alloy can product nearly complete shape memory effect. So, studies on NiMnInFe shape memory alloy have important significance on theory and practical applications.In this thesis, the effect of magnetic field on Ni5oMn34In14Fe2alloy phase transformation is studied. Based on the research method of the combination of theoretical derivation and experimental verification, this thesis mainly studies the determination of martensitic and austenite transformation temperature, the effect of magnetic field on phase transition and the plus-magnetic experimental. The tasks are listed out mainly on the below several aspects:(1) The crystal structure of Ni5oMn34In14Fe2alloy under the conditions of heating and cooling is analyzed by high energy x-ray diffraction experiment. Based on the analysis of diffraction pattern, the austenite is determined as L21structure, the lattice constant of austenite is determined as a=5.985339A. By measuring and calculating the magnified characteristics dot, the martensite phase determined as10M martensite.(2) By differential scanning calorimetry, the martensitic and austenite transformation temperature is determined, which are Ms=250K, Mf=240K, As=250K and Af=260K.(3) The research results show that the magnetic field intensity needed for induced phase transformation is decreased with the increased of temperature. Heating preservation and appling magnetic field when the temperature is lower than Mf, the diffraction mottling of martensite can complete recovery after demagnetization. However, because the driving force for martensite transformation cannot achieve the needed, diffraction mottling of martensite cannot complete recovery only under the temperature of Mf after demagnetization.(4) By the research of NisoMn34In14Fe2alloy at low temperature, high magnetic field along the direction of [100] can induce martensitic reverse transformation at low temperature, and the polycrystalline state is transformed into highly oriented state after demagnetization.