Study on superelasticity of nanocrystalline NiTiV memory alloys
NiTi based memory alloys have a narrow super-elastic temperature range(＜100 ℃),which limits their application range.In this paper,nanocrystalline(NC)Ni51Ti49V1(at.％)alloy wire was prepared by Ni-V co-doped NiTi through vacuum induction melting,forging,large deformation wire drawing and low tempera-ture annealing.The microstructure of the sample was characterized by transmission electron microscopy(TEM),and the superelasticity of the sample was characterized by universal tensile testing machine.The re-sults showed that Ni51Ti49V1 alloy consists of nanocrystalline with an average grain size of 13 nm.Tensile tests at different temperatures showed that the alloy exhibited excellent superelasticity in a wide temperature range from-40 ℃ to 100 ℃,and the superelastic temperature range was wider than that of NC NiTi alloy(25-100 ℃).In addition,the temperature dependence of the critical stress of the B2→B19'transformation(dσ/dT)de-creased from 5.6 MPa/℃ to 1.8 MPa/℃ with decreasing temperature.
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