The Effect of Specimen Dimension on Martensitic Transformation and Phase Stability in Ti-Ni Shape Memory Alloys

Sakamoto, H.; Meguro, Kouichi; Tanaka, Akihiro; Imai, Akira

doi:10.1051/jp4/199558581

Cited by 4 publications

(5 citation statements)

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“…There are cases where the width of the martensitic transition (M S − M F ) was found to increase with the grain size. 22 This suggests that the hindering effects associated to internal stresses can increase with size, a feature which might be consistent with our results. The influence of microstructure on the staircase effect in manganites obviously deserves further investigations.…”

Section: Discussionsupporting

confidence: 91%

Staircase effect in metamagnetic transitions of charge and orbitally ordered manganites

Hardy¹,

Hébert²,

Maignan³

et al. 2003

Journal of Magnetism and Magnetic Materials

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Section: Discussionsupporting

confidence: 91%

Staircase effect in metamagnetic transitions of charge and orbitally ordered manganites

Hardy¹,

Hébert²,

Maignan³

et al. 2003

Journal of Magnetism and Magnetic Materials

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“…In fact, the present author and coworkers have recently found through DSC measurement that the characteristics of thermoelastic MTs in some shape memory alloys have altered with specimen size (mass). 4,5,[15][16][17] Here, the specimen size concerned is of millimeter scale. No other researcher has systematically investigated the effect of specimen size on transformation behavior.…”

Section: Effect Of Scs On Characteristics Of Timts Through Specimen Sizementioning

confidence: 99%

“…The effect of specimen mass on transformation temperatures has thus far been investigated for transformations between B2 parent and B19' monoclinic martensite in a polycrystalline Ti-50 mol%Ni alloy, 15,16) between B2 parent and B19 orthorhombic martensite in a polycrystalline 49.5Ti-40Ni-10Cu-0.5Al (mol%) alloy, 17) between β 1 parent (D0 3type ordered structure) and β 1 martensite (18R 1 -type longperiod stacking-order [LPSO] structure in Ramsdell notation) in a single crystal of a Cu-13.4Al-4.2Ni (mass%) alloy, 4,5) and so forth. As a result, in any of these alloys, TIMT characteristics have been found to alter with specimen mass as follows.…”

Section: Effect Of Scs On Characteristics Of Timts Through Specimen Sizementioning

confidence: 99%

“…The variations of T * o have been, however, thus far elucidated to be caused by nonchemical energy G nonc * generated when martensite plates form at M s . 10,15) Here, the subscript * is appended to denote energy generated when a fraction f o of martensite plates form at M s . The present author and coworkers have already derived an equation T * o = ( H P→M + G P→M nonc * )/ S P→M which gives the variations of T * o with G P→M nonc * .…”

Section: Effect Of Scs On Characteristics Of Timts Through Specimen Sizementioning

confidence: 99%

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Distinction between Thermal and Stress-Induced Martensitic Transformations and Inhomogeneity in Internal Stress

Sakamoto

2002

Mater. Trans.

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A concept of inhomogeneous internal stress called shape change stress (SCS) was introduced in martensitic transformations (MTs). The SCS was considered to be required because martensite plates formed on cooling must deform the surrounding untransformed parent. The concept enabled successful elucidation of the reason for the progress of thermally induced MTs (TIMTs) with changing temperature and for that of stress-induced MTs (SIMTs) under constant stress on the basis of the Gibbs phase rule. Decreasing SCS with decreasing specimen size (mass) explained the downward shifts of experimental equilibrium temperatures T * o = (M s + A f)/2 with decreasing specimen mass m so far observed in the TIMTs of some shape memory alloys. Furthermore, the concept that no SCS is generated either in SIMTs or at the ultimate end of m = 0 in TIMTs rationalized the following observation on a monocrystalline Cu-13.4Al-4.2Ni (mass%) alloy. That is, the variations of M s and M f with m converged at the extrapolation to m = 0, and those of A s and A f also did; M # s = M # f and A # s = A # f (the superscript # indicates the transformation temperatures at the ultimate end of m = 0). The former coincided with T L (0) where the dependence of transformation stress σ L on temperature was extrapolated to stress zero, and the latter coincided with T U (0) where a similar extrapolation in the case of reverse transformation stress σ U was performed.

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“…1) However it has been reported that the features of the MPT in SMA thin films depend on the film thickness. 2,3) In order to use Ni-Ti in the thin film-state, it is therefore important to know, from both a fundamental and a technological point of view, if the properties of the MPT in Ni-Ti thin films differ from those observed in bulk materials and if a size effect occurs.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Resonance Studies of Martensitic Phase Transformation in Ni-Ti Shape Memory Alloys

2002

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Ni-Ti Shape Memory Alloys (SMA) are of great technological interest because they have the best shape memory behaviour of all SMA. Moreover, Ni-Ti thin films are considered to be one of the most promising solutions for the development of new microactuators. In order to use Ni-Ti in the thin film-state, it is therefore important to know if the properties of the martensitic phase transformation responsible for the shape memory effect are different in Ni-Ti thin films and in bulk materials. For that purpose, 61 Ni Nuclear Magnetic Resonance (NMR) measurements have been performed at very high magnetic field (14 T) in Ni-Ti bulk alloys as well as in thin films. The process of nucleation and growth of the R-phase and of the martensite in the different samples have been studied by means of a careful analysis of the 61 Ni NMR spectra recorded at different temperatures from T > R s to T < M f . The complex structure of the NMR spectra during phase transformation has been interpreted as a sum of contributions arising from the coexisting crystalline phases. The spectral deconvolution is very difficult to achieve because the NMR martensitic line of complex shape is partly superimposed on the austenitic line. However, additional NMR measurements in a 61 Ni enriched Ni-Ti bulk alloy allowed us to identify the microscopic interactions responsible for the martensitic line shape. With the help of this analysis it was then possible to determine the volume fraction of the different phases present at each temperature in the Ni-Ti bulk alloys and thin films. The NMR results showed that in Ni-Ti bulk alloys, where the R-phase transformation does not take place or is only partial, the martensitic transformation is not complete even at temperatures well below M f as determined by calorimetry. On the other hand, in thin films showing a well distinct two-step transformation via the R-phase no remaining austenite could be detected below the R f temperature.

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The Effect of Specimen Dimension on Martensitic Transformation and Phase Stability in Ti-Ni Shape Memory Alloys

Cited by 4 publications

References 0 publications

Staircase effect in metamagnetic transitions of charge and orbitally ordered manganites

Staircase effect in metamagnetic transitions of charge and orbitally ordered manganites

Distinction between Thermal and Stress-Induced Martensitic Transformations and Inhomogeneity in Internal Stress

Nuclear Magnetic Resonance Studies of Martensitic Phase Transformation in Ni-Ti Shape Memory Alloys

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