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Research On Microstructure、Pseudoelasticity And Corrosion Resistance Of TiNi(Cu、Mn)Alloy

Posted on:2013-05-15Degree:MasterType:Thesis
Country:ChinaCandidate:X J WanFull Text:PDF
GTID:2231330374464344Subject:Materials science
Abstract/Summary:PDF Full Text Request
NiTi alloy is the most widely used shape memory alloy, a third element is often added to broaden its scope of application, for example the cost of the alloy can be reduced by using copper(Cu) to replace nickel(Ni) partly, the addition of manganese(Mn) can reduce the phase transition temperature of the alloy, etc. In addition to the excellent shape memory effect, NiTi alloy is also possessed of the pseudoelasticity widely used in the engineering applications and the corrosion resistance widely used in the fields of biomedical. Therefore, there is practical guiding significance to study the pseudoelasticity and corrosion resistance of the NiTi alloy.In this paper, the effects of Cu、Mn and the aging time on the microstructure, compressed pseudoelasticity and corrosion resistance of the NiTi alloy have been investigated by using metallographic microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), automatic pressure testing machine and electrochemical workstation as the analysis and testing means.The results show that, after aging by450℃×(8or12or24)h, NiTi binary alloy is mainly B2body-centered cubic NiTi phase, TiNiCu and TiNiCuMn alloys are mainly B2body-centered cubic NiTi or CuNiTi2phase; the NiTi binary alloy and TiNiCu ternary alloy aged by450℃×12h can get the relatively uniform microstructure, the microstructure will become uniform with the aging time increased in TiNiCuMn alloy. In the alloy composition respect, NiTi binary alloy is the most uniform, Cu helps for the precipitation of the phase in the grains, and Mn will inhibit the particle phases diffusing from boundaries to the grains in a certain extent.Experiments show that, the NiTi alloys are possessed of pseudoelasticity. The integrity of the crystal structure will be undermined by the large particles precipitated phase in the matrix caused by element Cu, so the pseudoelasticity of NiTi alloy can not be improved by Cu addition. The size of precipitated phasse will increase with the Cu content increased and the pseudoelasticity will become worse; however, the pseudoelasticity has been improved in NiTi alloy within Cu and Mn additions, its performances are significantly better than NiTi binary alloy after a certain compression cycling conditions. But the introduction of dislocations and other defects will make the pseudoelasticity become worse.The electrochemical corrosion experiment in the0.9%NaCl (pH=7.4) saline showed that, NiTi binary alloy aged by450℃×8h has the best corrosion resistance among all corrosion specimens. In TiNiCu ternary alloy aged by450℃×8h, the corrosion resistance will decrease with the increase of Cu content, and its corrosion morphology is generally the sponge loose. In TiNiMn ternary alloy, the corrosion resistance of the over all performance is more stable, with little effect by aging time.
Keywords/Search Tags:NiTi alloy, copper, manganese, microstructure, pseudoelasticity, corrosion resistance
PDF Full Text Request
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