Study On The Shape Memory Behaviors Of NiTi Alloy Wire

NiTi shape memory alloy is a new functional material with good shape memory function.It plays an irreplaceable role in various fields and greatly promotes the development of world industry.In this paper,the phase transformarion behavior,microstructure,tensile properties and shape memory behavior of NiTi shape memory alloy wire with different Ni content under different heat treatments were studied systematically,which provided reference basis for the application of NiTi shape memory alloy wire.In this paper,the phase transformation behavior of NiTi memory alloy was studied by differential scanning calorimeter,the microstructure of NiTi shape memory alloy wire was observed by metallographic microscope,the tensile and shape memory properties of NiTi alloy wire were studied by electronic tensile testing machine equiped with environment studio.The results are as follows:1.With Ni content of NiTi alloy increases 0.1at.%,the phase transformation temperature of NiTi alloy decreases 10^oC.The heat treatment temperature had no significant influence on the phase transformation temperature,thermal hysteresis of Ni50Ti50 alloy,but had a greater influence on the phase transition temperature and thermal hysteresis of Ni_50.8Ti_49.2 alloy.2.Ti-rich NiTi alloy(for example Ni₅₀Ti₅₀)consists of B2?austenite phase?,Ti₄Ni₂O phase,while the Ni-rich NiTi alloy(for example Ni_50.8Ti_49.2)mainly consists of M phase?martensite phase?and Ti₄Ni₂O phase.3.As the Ni content of NiTi alloy increases,the?variation monotonicity decreases,and the?_s and?_b decrease first and then increase.For the Ni_50.8Ti_49.2 alloy wire under different heat treatments,with the temperature of heat treatment increases,the?increases first and then decreases.On the whole,it shows an upward trend for?s and a downward trend for?_b.4.With the increasing of tensile deformation,the recovery stress of Ni₅₀Ti₅₀0 alloy wire increases correspondingly during the heating process,and the recovery stress is greater than the tensile stress.When the tensile deformation reached 6%and then unload,during the heating-cooling cycles of Ni50Ti50 alloy wire,within 10 times thermal cycles,the temperature at which the constraint stress began to increase and began to decrease tended to be stable,and the recovery stress tended to be stable.5.A low rigidity NiTi alloy spring was fabricated by hot winding method.Compared with TiNiFe and TC4 alloys,which are also corrosion resistant materials,Ni50.8Ti49.2 alloy have better corrosion resistance in 3.5%NaCl solution and are more suitable for working under marine corrosive environment.