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The Structure Evolution, Phase Transformation and Shape Memory Behavior of Shape Memory Alloy with Low Nb Content

Author: YangYaZhuo
Tutor: YangShangLin
School: Harbin Engineering University
Course: Materials Science
Keywords: NiTiNb alloy Organizational structure Phase change characteristics Shape Memory Effect Transformation hysteresis
CLC: TG139.6
Type: Master's thesis
Year: 2005
Downloads: 199
Quote: 0
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Abstract


At present, at home and abroad in applied basic research and engineering applications are typical wide lag Ni 47 Ti 44 Nb 9 shape memory alloy However, the high cost of this alloy limits its application. The the Ni 47 Ti 44 Nb 9 alloy shape memory effect, the wide hysteresis effects from alloy NiTi matrix phase, so this article matrix phase component reference, the study low Nb (4.5at%) content of low-cost wide hysteresis shape memory alloy. In this paper, SEM, XRD, DSC, resistance - temperature tester under different temperature tensile tests and other testing techniques to study the low-Nb alloy Ni / Ti ratio of the impact of changes in its organizational structure and phase transition characteristics, analysis the mechanical behavior of the alloy, the amount of deformation of the transformation hysteresis and strain recovery rate of NiTiNb alloy wide hysteresis mechanism. Studies show that a low Nb content NiTiNb alloy is the NiTi matrix phase, β-Nb-phase and the oxide phase composition, and with the increase in the alloy of the Ni / Ti ratio of β-Nb phase reduction; β-Nb phase in the low-Nb alloy much lower than the number of Ni 47 Ti 44 Nb 9 alloy. The low Nb alloy phase change process for B 2 (?) B19, the phase transition temperature of the alloy with the Ni / Ti ratio of increase is reduced. Different ingredients NiTiNb alloy strain recovery rate comparison found that due to the irreversibility of the plastic deformation of the β-Nb phase, containing the β-Nb alloy phase NiTiNb even variable only 4% of the recovery rate can not reach 100%, and the β-Nb phase minimal NI of 49.6 a Ti 45.9 Nb 4.5 alloy should be variable is less than 8% deformation can be completely restored, and the small amount of deformation 16% Ni 49.6 Ti 45.9 Nb 4.5 alloy ratio Ni 47 the Ti 44 Nb 9 alloys have the better the shape memory effect. After pre-deformation, low Nb (4.5at%) the content NiTiNb shape memory alloy has wide transformation hysteresis. Since The deformation of improve Ni the 49.6 Ti 45.9 Nb 4.5 , Ni the 47 Ti 44 Nb 9 two alloy inverse martensitic phase transition stability results are similar, so that relatively NiTiNb β-Nb alloy wide contribution to the lag effect is very small, thus changing the alloy Nb solid solution in NiTi matrix of martensitic transformation kinetics the characteristic is NiTiNb alloy phase widens the main reason for lagging.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > The alloy learn with a variety of properties of alloys > Other special nature of the alloy > Shape Memory Alloys
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