Temperature dependence of superelastic stress in nanocrystalline NiTi shape memory alloy/Nb nanowire composite
NiTi shape memory alloys have been widely used due to their superelasticity.However,the superelastic stress of martensitic transformation in traditional NiTi alloys rapidly decreases with the decrease of temperature(6-7 MPa/K),significantly limiting their application in a wide temperature range.This study obtained nanocrystalline NiTi/Nb wire through melting,forging and wire drawing,and then studied the microstructure,phase transformation behavior and superelastic properties of the wire using transmission electron microscopy,differential scanning calorimeter and tensile testing machine.The results indicate that the average grain size of NiTi alloy in nanocrystalline NiTi/Nb wire is 14 nm,and the wire undergoes thermally induced B2→R phase transition and R→B2 phase transition during cooling and heating processes,respectively.In the temperature range of 328-376 K,the average value of superelastic stress for stress induced B2→B19′ transformation is 1002 MPa,and the temperature dependence of superelastic stress is 4.1 MPa/K.
NETL
NSTL
万方数据
维普
