Current Density Contour Map of TiNi Shape Memory Alloy in Sulfate Solutions

2007 ◽  
Vol 342-343 ◽  
pp. 569-572
Author(s):  
Seung Chan Na ◽  
Seung Ho Park ◽  
Woon Suk Hwang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Density ◽  
Sodium Sulfate ◽  
Chloride Ion ◽  
Localized Corrosion ◽  
Tini Alloy ◽  
Contour Map ◽  
Sulfate Solutions ◽  
Density Contour

In this study, a current density contour map of TiNi shape memory alloy in sodium sulfate solutions was constructed by potentiodynamic polarization technique. The current density contour map of TiNi alloy, constructed in a 0.5 M sodium sulfate solution over the pH range 1 to 13 at 37oC, showed only hydrogen evolution region, passive region, and oxygen evolution region. The localized corrosion region did not exist and the susceptibility of localized corrosion was not exhibited. We also investigated the effects of chloride ions on the pitting corrosion of TiNi alloy in sodium sulfate solutions. Pitting corrosion occurred with addition of 0.2 M NaCl in a sulfate solution. And it was observed that pitting potential got lower as the concentration of chloride ion went up. However, repassivation potential was not affected by the addition of chloride ion up to 0.5 M. It is concluded that a TiNi shape memory alloy exists as a passive state and a good corrosion resistance in sulfate solutions over the pH range 1 to 13, and the sulfate ion performs a role of inhibiting localized corrosion in chloride environment.

Current Density Contour Map of TiNi Shape Memory Alloy in Simulated Physiological Solutions

2007 ◽  
Vol 342-343 ◽  
pp. 573-576
Author(s):  
Woon Suk Hwang ◽  
Seung Chan Na ◽  
Jeong Ja Lee
Keyword(s):  
Sodium Chloride ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Density ◽  
Localized Corrosion ◽  
Tini Alloy ◽  
Contour Map ◽  
Chloride Solutions ◽  
Sodium Chloride Solutions ◽  
Density Contour

In order to investigate the corrosion behavior of TiNi shape memory alloy, especially electrochemical behavior of pitting and crevice corrosion in a human body, current density contour(CDC) map of TiNi alloy was constructed by potentiodynamic polarization technique in simulated physiological sodium chloride solutions of pH ranging from 1 to 13 at 37oC. Morphology of pits and corrosion products in sodium chloride solutions of various pH were analyzed by SEM and EDX, and susceptibility and mechanism of localized corrosion were also discussed.

The Effect of Vacancy on the Phase Stability of TiNi Shape Memory Alloy from First-Principle Calculation

2011 ◽  
Vol 687 ◽  
pp. 528-532
Author(s):  
Bin Yue ◽  
Yan Li ◽  
Fei Zhang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Phase Stability ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Tini Alloy ◽  
First Principle ◽  
Generalized Gradient ◽  
First Principle Calculation ◽  
Formation Enthalpies

The effect of vacancy on the phase stability of TiNi shape memory alloy has been investigated by the first-principle method based on the density functional theory with generalized gradient approximation. The formation energy, formation heat, formation enthalpy per atom and density of states (DOS) of TiNi alloy with and without vacancy are calculated. The results indicate that the favorable point defect is Ni vacancy in both B2 and B19’ phases of TiNi alloy. The existence of vacancy increases the formation enthalpies per atom difference and thus decreases the phase stability. The DOS values at Fermi level of martensitic phases are lower than that of austenite phases in both perfect TiNi and TiNi with Ni vacancy, indicating the natural transformation from austenite to martensite upon cooling.

Effects of High Temperature ECAE Process on Microstructures and Martensitic Transformation of TiNi Shape Memory Alloy

2006 ◽  
Vol 503-504 ◽  
pp. 1013-0 ◽  
Author(s):  
Chao Ying Xie ◽  
Z.G. Fan ◽  
Z.H. Li ◽  
G.Q. Xiang ◽  
X.H. Cheng
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Tini Alloy ◽  
Behavior Changes ◽  
Transformation Behavior ◽  
Coarse Grains ◽  
Short Annealing

Microstructures and transformation behavior of TiNi shape memory alloy after high temperature ECAE process have been investigated. It is found that the initial coarse grains were refined after high temperature ECAE processes and short annealing at 750°C. Transformation temperatures of TiNi alloy sharply decreased after two ECAE processes, rose obviously when annealed at 750°C for 5min, and quickly rose back after annealing at 500°C for 2 hours. Reasons for phase transformation behavior changes have been discussed.

INFLUENCE OF POROSITY ON SHAPE MEMORY BEHAVIOR OF POROUS TiNi SHAPE MEMORY ALLOY

2008 ◽  
Vol 01 (03) ◽  
pp. 215-219 ◽  
Author(s):  
JIANYU XIONG ◽  
YUNCANG LI ◽  
PETER D. HODGSON ◽  
CUI'E WEN
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Tini Alloy ◽  
Compression Tests ◽  
X Ray Diffraction ◽  
Recoverable Strain ◽  
Strain Concentration ◽  
X Ray ◽  
Shape Memory Behavior ◽  
Porous Ti

Porous Ti -50.5at.% Ni shape memory alloy (SMA) samples with a range of porosities were prepared by spacer sintering. The porous structure of the alloy was examined using scanning electron microscopy (SEM). The phase constituents of the porous TiNi alloy were determined by X-ray diffraction (XRD). The shape memory behavior of the porous TiNi alloy was investigated using loading–unloading compression tests. Results indicate that the porous TiNi alloy exhibits superelasticity and the recoverable strain by the superelasticity decreases with the increase of porosity. After a prestrain of 7%, the superelastically recovered strains for the porous TiNi alloy samples with porosities of 46%, 59%, 69% and 77% are 2.0%, 1.8%, 1.5% and 1.3%, respectively. The pores in the TiNi alloy samples cause stress/strain concentration, as well as crack initiation, which adversely affect the shape memory behavior of the porous TiNi alloy.

scholarly journals Current Density Contour Map

1982 ◽  
Vol 31 (6) ◽  
pp. 429-430 ◽  
Author(s):  
Katsuhisa SUGIMOTO
Keyword(s):  
Current Density ◽  
Contour Map ◽  
Density Contour

Investigation on Ce Addition on Microstructure and Martensitic Transformation of a Ti51Ni49 Shape Memory Alloy

2016 ◽  
Vol 852 ◽  
pp. 28-32
Author(s):  
Ai Lian Liu ◽  
Nan Nan Mao ◽  
Jia Wen Xu ◽  
Wei Cai
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Ternary Alloys ◽  
Tini Alloy ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
The Matrix ◽  
One Step ◽  
Electronic Microscope

The effect of rare earth element Ce addition on the microstructure and martensitic transformation behavior of Ti51Ni49 shape memory alloy was investigated by scanning electronic microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the microstructure of TiNiCe ternary alloy consists of Ti2Ni phase, CeNi phase and the matrix. One-step martensitic transformation is observed in quenched TiNiCe ternary alloys, which is the same as that in quenched TiNi binary alloys. The martensitic transformation temperatures of Ti-rich TiNi alloy hardly increase with Ce addition.

Unusual Multistage Martensitic Transformation in TiNi Shape Memory Alloy after Thermal Cycling

2013 ◽  
Vol 738-739 ◽  
pp. 372-376 ◽  
Author(s):  
Aleksey Sibirev ◽  
Sergey Belyaev ◽  
Natalia Resnina
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Temperature Interval ◽  
Defect Structure ◽  
Tini Alloy ◽  
Thermal Cycles ◽  
Unusual Phenomenon ◽  
Kinetics Of

Variation in kinetics of martensitic transformation, in an equiatomic TiNi shape memory alloy, during thermal cycles was investigated. Samples annealed at 500 °C for 1 hour were subjected to repeated thermal cycles, through the temperature range of martensitic transformation. Unusual 4-stage martensitic transformation during cooling after 30 thermal cycles was observed. Moreover, a new unusual phenomenon was found in the preliminary thermal cycled TiNi alloy. It was observed that variation in the highest temperature Th of thermal cycles temperature interval resulted in the redistribution of released heat among four calorimetric peaks, observed on cooling. It was found that if the Th temperature did not exceed 240 °C the variation in kinetics was repeatable, and determined only by the value of Th. It was assumed that the defect structure induced on preliminary thermal cycling changes reversibly on cooling and heating.

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