International Journal of Applied Electromagnetics and Mechanics - Volume 23, issue 1-2

Article Type: Editorial

Abstract: Preface to the E-MRS Fall Meeting 2005 special issue.

DOI: 10.3233/JAE-2006-732a

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 1-1, 2006

Authors: Pieczyska, E.A. | Gadaj, S.P. | Nowacki, W.K. | Tobushi, H.

Article Type: Research Article

Abstract: Martensitic and reverse transformations in TiNi shape memory alloy subjected to tension test at room temperature are investigated using a thermovision camera. Stress relaxation stages during the loading and unloading branches are induced, respectively. A very large stress drop, caused by the phase transformation, is observed during the stress relaxation in both the course of loading and unloading, while, for the temperature-controlled test, in the unloading branch the stress increases under constant strain; due to the …recovery. The non-uniform temperature distribution reflecting the inhomogeneous phase transformation at its initial stage is observed to start again at the end of the relaxation break and develop during the reloading process. Show more

Keywords: TiNi shape memory alloy, phase front, stress relaxation

DOI: 10.3233/JAE-2006-713

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 3-8, 2006

Authors: Nam, Tae-hyun | Yu, Cheo-am | Lee, Yun Jung | Liu, Yinong

Article Type: Research Article

Abstract: Phase transformation and deformation behavior of temperature-gradient annealed (TGA) equiatomic Ti-Ni alloy wires were investigated by means of differential scanning calorimetry (DSC), thermal cycling under constant load and tensile testing. TGA treatment in a temperature range of 658∼823 K caused variations of 10 K in T_{R} * and 14 K in M_{s} along the length of the specimen. Temperature dependence of specimen elongation (dε/dT) of TGA treated Ti-Ni alloy …wires was in the range of 0.12∼0.43%/K depending on annealing temperatures. The lowest dε/dT was obtained in the sample annealed in the temperature range of 658∼713 K. The stress for martensite reorientation remained nearly constant for the specimen annealed in the temperature range of 740∼823 K, whereas that for the specimen annealed in the temperature range of 658∼740 K increased continuously with increasing strain. Show more

Keywords: Ti-Ni shape memory alloy, martensitic transaformation, temperature gradient annealing, actuator, proportional control

DOI: 10.3233/JAE-2006-716

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 9-15, 2006

Authors: Yang, Zhiqing | Schryvers, Dominique

Article Type: Research Article

Abstract: Composition gradients surrounding Ni_4 Ti_3 precipitates in a Ni_{51} Ti_{49} B2 austenite matrix are investigated by a combination of analytical TEM techniques, including electron energy loss spectroscopy (EELS), energy filtered TEM (EFTEM) and energy dispersive X-ray spectroscopy (EDX). A Ni depleted zone in the surrounding matrix was detected. The size and concentration change of the depletion zone compensate very well for the excess Ni in the …precipitate. Since different precipitates are often formed in nanoscale proximity, depletion zones from different precipitates can enforce one another in certain regions. A new quantification technique of EELS confirmed the 4:3 atomic ratio between Ni and Ti for the precipitate. No Ni-rich zone in the vicinity of grain boundaries was detected in the solution-treated samples. Show more

Keywords: NiTi, precipitate, EELS, EFTEM, EDX

DOI: 10.3233/JAE-2006-711

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 17-24, 2006

Authors: Paula, A.S. | Mahesh, K.K. | dos Santos, C.M.L. | Canejo, J.P.H.G. | Fernandes, F.M. Braz

Article Type: Research Article

Abstract: In the present study, the phase transformations in the Ti-rich (51.0 at% Ti–Ni) NiTi Shape Memory Alloy (SMA) was analyzed using four characterization techniques: Differential Scanning Calorimetry (DSC), Electrical Resistivity (ER), Dilatometry and X-Ray Diffraction (XRD). During the phase transformations various physical parameters of the material are modified and each technique senses different physical phenomena. In order to distinguish the different types of sequences (one-step versus two-step) the observations are discussed highlighting …the capability of each technique to analyze the phase transformations in NiTi SMAs. Show more

Keywords: Shape memory effect, transformation steps, DSC, electrical resistivity, dilatometry, XRD

DOI: 10.3233/JAE-2006-727

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 25-32, 2006

Authors: Besseghini, Stefano | Villa, Elena | Portman, Jenni

Article Type: Research Article

Abstract: It is well-known that the special properties of NiTi shape memory alloys strongly depend on their microstructure and their thermomechanical state. DSC and mechanical tests (stress-strain vs temperature) do provide extensive information on the transformation temperatures and on the pseudoelastic effect: a Dynamic Mechanical Analyzer (DMA) is further able to investigate even more transition effects, because it makes it possible to study the transition temperatures in both stressed and unstressed conditions over a …wide temperature range (−150°C; 600°C). Moreover, through dynamic experiments one can to analyse the linear mechanical response and the viscoelastic properties in different ranges of strains and frequency. In this work we measure the response of NiTi in the austenitic and rhombohedral phase. We test the material both in isothermal condition over a frequency range and at a constant frequency over a temperature ramp. The NiTi samples used were Ni50.5at%Ti wires, 80 μm in diameter, thermally treated at 450°C for 1.8 Ks. Show more

Keywords: Shape memory alloys, NiTi, DMTA, DMA

DOI: 10.3233/JAE-2006-728

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 33-38, 2006

Authors: Peradze, T. | Stamateli, I. | Cederstrom, J. | Berikashvili, T. | Razov, A. | Gorgadze, K.

Article Type: Research Article

Abstract: The degree of recoverable strain, reactive stress and pseudoelasticity of some Ti-Ta-Zr alloys were investigated. The measurement technique involved differential calorimetry, estimation of friction and evaluation of recoverable torsion strain. The alloys were quenched from different temperatures of the β-phase area and subjected to additional thermal and mechanical treatment required for subsequent examination. The degree of recoverable strain was measured on custom-made unit. The samples have been heated by electrical current and …using a furnace. Initial deformation of the specimens was achieved by torsion. For all of the alloys the shape recovery was not less than 90–98% for initial strain up to 7–9%. M_{s} and A_{s} values for the alloys range in 298–433 K and 523–673 K interval. These allowed to conventionally consider the shape memory effect in these alloys as a "high temperature" (respectively to TiNi) phenomenon. The values of the reactive stress induced by reverse martensite transformation in the alloys was measured to be 300–550 MPa. After 3–4 cycles the pseudoelasticity of the alloys (strain-stress cycled at room temperature), for the initial strain – 3.5–4%, comes up to 100%. Show more

Keywords: Shape memory effect, Ti-Ta-Zr alloys, reactive stress, superelasticity

DOI: 10.3233/JAE-2006-730

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 39-43, 2006

Authors: Kakeshita, Tomoyuki | Fukuda, Takashi

Article Type: Research Article

Abstract: We have made an energy evaluation for the rearrangement of martensite variants (RMV) under a magnetic field using four types of ferromagnetic shape memory alloys: an Fe-31.2at. %Pd with so-called fct martensite, a Ni_2 MnGa with the 10 M martensite, a Ni_{2.02} Mn_{1.09} Ga_{0.89} with the 14 M one and a Ni_{2.14} Mn_{0.92} Ga_{0.94} with the 2 M one. The RMV by a …magnetic field occurs at any temperature for the Fe-31.2Pd and the 10 M martensite. However, it occurs in a limited temperature range for the 14 M martensite and does not occur at any temperature for the 2 M martensite. The reason of such different behavior is quantitatively explained by evaluating two shear stresses: the magnetic shear stress acting across a twinning plane τ_{mag} , and the stress required for the twinning plane movement τ_{req} . That is, by comparing the value of τ_{mag} and τ_{ req} thus evaluated, we have confirmed that the following condition is universal regardless of temperature, field direction and structure of the martensite phase: the value of τ_{mag} is larger than τ_{req} when the RMV occurs by magnetic field and vice versa. Show more

DOI: 10.3233/JAE-2006-715

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 45-50, 2006

Authors: Sakon, T. | Takaha, A. | Motokawa, M. | Fukuda, T. | Kakeshita, T.

Article Type: Research Article

Abstract: A system for the simultaneous measurement of magnetization and magnetic strain, which is designed to be used in a pulsed magnetic field, has been developed. In this system, a capacitor on a sample is used and its capacitance changes with the displacement of a sample due to the strain on the sample in a magnetic field. Using this system, we have studied the magnetization and magnetic field-induced strain (MFIS) of the martensitic metallic compound Fe-31.2%Pd (at. …%) at temperatures down to 80 K in martensite phase, which is much lower than the martensitic transformation temperature T_{M} =230 K. A substantial MFIS has been measured under a pulsed magnetic field with the time constant 6 ms, which corresponds to 80 Hz in frequency. Show more

Keywords: Shape memory alloy, magnetic field-induced strain, capacitance method, pulsed magnetic field

DOI: 10.3233/JAE-2006-712

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 51-58, 2006

Authors: Jee, K.K. | Han, J.H. | Kim, Y.B. | Jang, W.Y.

Article Type: Research Article

Abstract: In this work, a new method of measuring volume fraction of ε martensite formed both by cooling and deformation using volume change and endothermic heat on ε→ γ transformation, respectively. The variation in the amount of ε with grain size is determined for an Fe-21Mn alloy, and its influence on shape memory effect is investigated. As grain size increases, the amount of ε martensite forming on cooling increases. However, with a decrease …in grain size, more ε is induced by deformation, improving shape memory effect. Show more

Keywords: Fe-Mn alloy, volume fraction of ε martensite, shape memory effect, DSC

DOI: 10.3233/JAE-2006-717

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 23, no. 1-2, pp. 59-64, 2006