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The phase stability of intermetallic compounds of Co3X has been discussed with a focus on the γ' phase of Co3Al, Co3W and Co3(Al, W) with the L12 structure. The critical temperatures of the γ' phase of Co3Al, Co3W and Co3(Al, W) compounds are estimated to be about 870 , 980 and 1076 , respectively. The effect of alloying elements on the Co-Al-W -base alloys was found to be very similar to that of Ni-base superalloys, where Ti, Ta, Nb and V are the γ' stabilizing elements, while Mn, Fe and Cr are the γ' forming elements. The mechanical properties of Co-Al-W-base alloys were also found to be similar to those of Ni-base alloys. In particular, the flow strengths of Co-Al-W-base alloys at temperatures above 800 were comparable or higher than those of Ni-base superalloys, which implies that the Co-base superalloys strengthened by the γ' phase have great potential as a new type of high-temperature alloys.

The cobalt-rich portions of the Co-Si and Co-Ge systems between 700 and 1100°C have been investigated by means of electron probe microanalysis. The equilibrium between α(f.c.c.) and e(c.p.h.) phases has been detected mainly by the diffusion couple technique, and it has been clarified that the c.p.h. phase is stable up to temperatures greater than 1100 °C in both the systems. It has also been found that the Co 3 Ge phase, probably having an A 15-type structure, exists somewhere between about 770 and 636 °C, being in equilibrium with the e and βCo 5 Ge 3 phases.

Phase constitutions of Fe-(20-30)wt%Mn-(0-10)wt%Al-C alloys have been investigated by electron probe microanalysis and transmission electron microscopy. The phase relations between austenite and perovskite carbide, (Fe, Mn)3AlC in the temperature range of 900-1 200°C have been carefully examined. An L12-type ordered structure, which was reported to be formed in rapidly solidified alloys as a metastable phase has not been detected in specimens aged at temperatures above 600°C.

Sn-Ag-Cu base solders are the most potential candidates to substitute of Sn-Pb eutectic solder. Gold (Au) coatings are used to protect conductor surface from oxidation and thereby to promote the solderability, and nickel (Ni) is often used as a diffusion barrier layer between lead-free solders and substrates to restrict the growing of intermetallic compound layers. And the gold and nickel also are added to the Pb-free solders to improve their performance. In the present work, the thermodynamic calculations of phase equilibria in the Sn-Ag-Cu-Ni-Au system were carried out using the CALPHAD method. Some examples of application are presented, and it is shown that the CALPHAD method is a good tool to design Pb-free solders and understand the interfacial reaction.

Publisher Summary This chapter begins with introducing the widely used methods involving thermal analysis such as differential scanning calorimetry, electrical resistivity, and X-ray diffraction. These methods measure the order–disorder transition temperature by monitoring a thermal, physical, or structural change during heating and cooling of an alloy. The chapter then focuses on two alternative methods that extract the order–disorder transition concentration from diffusion couples. The singular point method and the concentration gradient method developed in recent years can determine the critical ordering concentration and the solubility line of coherent ordering at a fixed temperature thus allowing order–disorder transitions to be accurately defined on isothermal sections. The experimental procedure for the concentration gradient method consists of the four steps: formation of a continuous concentration profile in a diffusion-couple (DC) specimen by annealing at a high temperature; formation of precipitation or anti-phase domain (APD) zone in the diffusion layer of the as-annealed DC, due to ageing followed by quenching; microstructural observation in the vicinity of the precipitation or APD zone by transmission electron microscopy or scanning electron microscopy; construction of a concentration–penetration profile using energy dispersive spectroscopy or electron-probe microanalysis and determination of the boundary concentrations between the single-phase-(or no APD) zone and two-phase (or APD) zone.

We have identified cobalt-base superalloys showing a high-temperature strength greater than those of conventional nickel-base superalloys. The cobalt-base alloys are strengthened by a ternary compound with the L1 2 structure, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\gamma}^{{^\prime}}\) \end{document} Co 3 (Al,W), which precipitates in the disordered γ face-centered cubic cobalt matrix with high coherency and with high melting points. We also identified a ternary compound, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\gamma}^{{^\prime}}\) \end{document} Ir 3 (Al,W), with the L1 2 structure, which suggests that the Co-Ir-Al-W–base systems with \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\gamma}+{\gamma}^{{^\prime}}\) \end{document} (Co,Ir) 3 (Al,W) structures offer great promise as candidates for next-generation high-temperature materials.

Magnetic and half-metallic properties of ${\mathrm{Co}}_{2}({\mathrm{Cr}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x})\mathrm{Ga}$ Heusler alloys have been investigated. In the entire concentration range, the $L{2}_{1}$-type ordered phase is obtained. The saturation magnetic moment ${M}_{s}$ at $4.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $x=0.0$ $(\ensuremath{\equiv}{\mathrm{Co}}_{2}\mathrm{Cr}\mathrm{Ga})$ is $3.01{\ensuremath{\mu}}_{B}∕\mathrm{f.u.}$, in agreement with the generalized Slater-Pauling line and consistent with the theoretical value. The experimental value of ${M}_{s}$ increases with increasing $x$, slightly larger than that of the theoretical value above $x=0.60$. The Curie temperature ${T}_{C}$ also increases with $x$, and qualitatively accords with the theoretical values estimated from the effective exchange constant ${J}_{0}$. The present theoretical results disclose that not only the $L{2}_{1}$-type ordered phase but also the $B2$-type phase exhibits high values of the spin polarization ratio $P$ in a low concentration range of $x$. The ratio $P$ of the $L{2}_{1}$- and $B2$-type phases decreases with increasing $x$, because the large peak of the density of states at the Fermi energy for Cr in the majority spin band becomes smaller and a strong hybridization between $\mathrm{Co}\text{\ensuremath{-}}3d$ and $\mathrm{Fe}\text{\ensuremath{-}}3d$ makes a gap narrower in the minority spin band.

The effect of applied strain on martensitic transformation in a superelastic Ti(46.4)Ni(47.6)Nb(6.0) alloy at room temperature was investigated by tensile tests, differential scanning calorimetry measurements, and X-ray diffraction. Reverse transformation starting (A(s)) and finishing (A(f)) temperatures increased with the application of tensile-strain over 13%, the undeformed specimen showing A(s) = -29.2 degrees C and A(f) = 17.9 degrees C, while the 13% predeformed alloy exhibited A(s) = 37.1 degrees C and A(f) = 40.2 degrees C. Furthermore, the values of the A(s) and A(f) for the predeformed alloy almost recovered to those of the undeformed alloy when heated to about 42 degrees C and then showed superelasticity again at room temperature. This characteristic is significant for application in sensors, actuators, and medical devices. Especially, medical stents with such qualities show promise as a new class of self-expandable stents with both excellent mountability and deliverability.

Large magnetic-field-induced strains1 have been observed in Heusler alloys with a body-centred cubic ordered structure and have been explained by the rearrangement of martensite structural variants due to an external magnetic field1,2,3. These materials have attracted considerable attention as potential magnetic actuator materials. Here we report the magnetic-field-induced shape recovery of a compressively deformed NiCoMnIn alloy. Stresses of over 100 MPa are generated in the material on the application of a magnetic field of 70 kOe; such stress levels are approximately 50 times larger than that generated in a previous ferromagnetic shape-memory alloy4. We observed 3 per cent deformation and almost full recovery of the original shape of the alloy. We attribute this deformation behaviour to a reverse transformation from the antiferromagnetic (or paramagnetic) martensitic to the ferromagnetic parent phase at 298 K in the Ni45Co5Mn36.7In13.3 single crystal.

$L{1}_{0}$-type FePd single crystals with a high order degree were prepared by ordering under compressive stress. Experimental and theoretical investigations on the relation among the axial ratio, $d$ electron number and magnetocrystalline anisotropy energy (MAE) in $L{1}_{0}$-type FePd single crystals have been carried out. In the concentration dependence of the lattice constants, the $a$ axis exhibits a strong dependence, compared with that of the $c$ axis. As a result, the ratio of $c∕a$ decreases with increasing Pd concentration. The uniaxial magnetocrystalline anisotropy constant ${K}_{U}$ at the equiatomic composition is evaluated to be $2.1\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.3em}{0ex}}\mathrm{erg}∕{\mathrm{cm}}^{3}$ at $4.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and $1.7\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.3em}{0ex}}\mathrm{erg}∕{\mathrm{cm}}^{3}$ at $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The MAE becomes weaker as the ratio of $c∕a$ is apart from unity at higher Pd compositions. The calculated results by the first principles calculations with the LMTO-ASA including the spin-orbit coupling for the MAE of $L{1}_{0}$-type ${\mathrm{Fe}}_{50}{\mathrm{Pd}}_{50}$ are in accord with the present experimental results. The increase in the $d$ electron number due to the increase of the Pd concentration facilitates the decrease of the MAE, cooperating with the decrease in the axial ratio $c∕a$.

Ti–Zn phase diagram and layers growth kinetics, have been studied at 500, 600 and 900 °C. Linear growth has been observed. The calculated values of the growth constants K G are: at 500 °C, K G =(7.5±0.3)×10 −9 m s −1 ; at 600 °C, K G =(8.0±0.2)×10 −9 m s −1 . An indication about the presence of a formerly unknown compound (Ti 2 Zn 3 ) has been found out by electron microprobe analyses and optical microscopy. Homogeneity ranges (probably metastable) have been observed for some phases that are considered to be stoichiometric.

A new type of medical guide wire with functionally graded hardness from the tip to the end was developed with the use of Cu-Al-Mn–based alloys. The superelasticity (SE) of the Cu-Al-Mn–based alloys in the tip is drastically improved by controlling the grain size, whereas the end of the wire is hardened using bainitic transformation by aging at around 200–400 °C. Therefore, the tip of the guide wire shows a superelasticity and its end has high stiffness. This guide wire with functionally graded characteristics shows excellent pushability and torquability, superior to that of the Ni-Ti guide wire. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 64–69, 2004

Effect of the magnetic field on the martensitic transformation of Co-Ni-Al single-crystal was investigated by differential thermal analysis (DTA) and the in-situ microstructure observation under magnetic field. The martensitic transformation temperatures Ms and Mf of the Co34.5Ni35.5Al30 single-crystal specimen showing the martensitic transformation from the paramagnetic austenite (B2) to the ferromagnetic martensite slightly increased under the magnetic field and those temperature shifts were about 1.3°C at 1.0T. It was also observed in the Co34.5Ni35.5Al30 single-crystal specimen that the phase boundaries between the austenite and the martensite slightly move by applying the magnetic field of 1.0T. These results are discussed on the basis of a thermodynamic stabilty of the martensite phase under the magnetic field. The martensitic and the magnetic transformation behaviors of the Ni-Al-Co alloys are also reviewed.

Recent progress on the database of calculated phase diagrams in micro-soldering alloy systems, which consist of Pb, Bi, Sn, Sb, Cu, Ag, In and Zn, is presented. Experimental determination of phase equilibria was conducted in several binary, ternary and quaternary systems by DSC, EDX and X-ray diffraction techniques. Based on these experiments, as well as on previous data on phase diagrams and thermo-chemical properties such as activity, heat of mixing and enthalpy of formation, the various thermodynamic parameters for describing the Gibbs energies of the different constituent phases were optimized and evaluated by the CALPHAD (calculation of phase diagrams) method. The database provides key information on liquidus and solidus surfaces, isothermal and vertical section diagrams, and mole fractions of the phase constitutions of multi-component soldering alloys. Thermodynamic properties of the surface tension and viscosity of the liquid phase can also be predicted. Moreover, a nonequilibrium solidification process using the Scheil model was simulated. Several phase diagrams of Pb-bearing and Pb-free solders are presented. The database is expected to be a powerful tool and an indispensable resource for the development of new Pb-free solders.

Order–disorder phase transition temperature from L21 to B2 phase, [Formula: see text], in Co -based Heusler alloys was systematically investigated based on the Braggs–Williams–Gorsky (BWG) approximation. Because height of [Formula: see text] closely correlates to phase stability of the L21 phase, confirmation of [Formula: see text] would be a key to obtain a highly ordered L21 phase. From modification with the BWG approximation it was shown that the degree of order indicated temperature dependence, namely, the degree of order decreased above around 0.6 [Formula: see text] and reached zero at [Formula: see text]. Therefore, it should be better to select the Co -based Heusler alloys with a higher value of [Formula: see text] if the higher degree of order in the L21 phase is desired by thermal annealing at as low temperature as possible. From powder neutron diffraction (ND) studies of Co 2Y Ga (Y = Ti , V , Cr , Mn and Fe ) alloys it was actually confirmed that materials with higher value of [Formula: see text] indicated higher degree of order even in the same annealing temperature. Studies for the phase state in Co – Ti – Fe – Ga films also showed that a height of [Formula: see text] concretely correlated to the phase stability of the L21 phases, that is, the specimen with higher value of [Formula: see text] was easy to obtain with a higher degree of order.

The utilization of phase diagrams on the microstructural control in iron-base alloys are presented focusing on solidification processes, low alloy steels, stainless steels and functional steels. It is shown that the recent progress in the computational approach for thermodynamic properties and phase diagrams have contributed significantly to progress in alloy design and microstructural control.

The evolution of sulfide morphology in the Fe- (0.3 to 18) mass% Cr -0.3 mass% S alloys during solidification and its modification by additions of elements such as Mn, Ti, Zr and C have been investigated by means of optical microscopy, scanning electron microscopy and X-ray diffraction. The sulfide morphologies in the Fe-Cr-S ternary alloy are classified under three types: (i) cellwall (ii) fine particle and (iii) globular sulfides. The iron-rich cellwall sulfide is formed in the Fe-(0.3-1) %Cr-0.3 %S alloys. This sulfide morphology changes to the globular type with increasing Cr content and the size of that is more than 51gm. Fine sulfide particles of size smaller than 2 gtm also coexist in the Fe-(0.3-5) %Cr-0.3 %S alloys. Zr or Ti additions change this morphology from the globular type to the rod-like type in the Fe-18 %Cr-0.3 %S alloy, but Mn addition does not have the same effect. The mechanism of the formation of different sulfide morphologies is discussed on the basis of phase diagram information.

Due to the close similarity between the common forms of ontology specification and classes in object-oriented systems, a set of object-oriented classes in a domain may provide the skeleton of the ontology of the domain. An object-oriented design for phase diagram databases has been made with special attention to this. Through the description of the analysis and coding of phase diagrams, the nature of the task of ontology construction is illustrated.

Magnetization and thermoelectric power (Seebeck coefficient) S of the magnetic shape memory compound Ni 50 Mn 36 Sn 14 were measured in the temperature T range from 4.2 to 330 K under magnetic fields up to 17 T. In 50 K T S has a negative sign, indicating that electron-type carriers dominate in this compound. The anomaly of the S – T curve closely relates to the magnetic and structural phase transition and the negative S value is enhanced by a magnetic field.

The B2/L21 order–disorder and magnetic transitions in Co2YGa (Y=Ti, V, Cr, Mn, Fe) alloys were investigated by electron probe microanalysis (EPMA), differential scanning calorimetry (DSC) and vibrating sample magnetometry (VSM). It was confirmed that the B2/L21 order–disorder transition temperature for the Co2YGa (Y=Ti, V, Cr) alloys monotonically decreases with increasing electron concentration of the Y site, whereas that of the Co2YGa (Y=Mn, Fe) alloys is almost constant at 1100 ± 100 K. On the other hand, the Curie temperature TC of all the alloys rises almost monotonically with increasing electron concentration of the Y site.

In order to clarify the structural properties of a novel ferromagnetic shape-memory alloy Ni 50 Mn 36 Sn 14 in magnetic fields, we have carried out high-field X-ray powder diffraction measurements under magnetic fields up to 5 T in the wide temperature range from 8 to 300 K. In this work, we confirmed that magnetic field induces the reverse martensitic transformation in Ni 50 Mn 36 Sn 14 at the vicinity of 220 K.

Normally, shape memory effect (SME) is obtained by the reverse martensitic transformation, therefore only induced by heating a sample from the deformed martensite phase. In this study, we report a phenomenon of cooling-induced SME, observed in a Co2Cr(Ga,Si) Heusler alloy, where the normal heating-induced SME can be obtained at the same time. The cooling-induced SME is attributed to an abnormal martensitic transformation in Co2Cr(Ga,Si) Heusler alloy. Moreover, an inverse temperature dependence of superelastic stress was also observed. The discoveries of these phenomena provide application possibilities for shape memory alloys, especially at low temperatures.

Experimental and numerical works are reported to assess the cyclic response of concrete beams reinforced with superelastic alloy (SEA) bars. The feasibility of newly developed Cu–Al–Mn SEA bars, characterized by large recovery strain, low material cost and high machinability, is examined as partial replacements for conventional steel bars, in order to reduce residual cracks in structures during and after intense earthquakes. Four-point reverse cyclic bending tests were done on one-third scale concrete beams comprising three different types of specimens—conventional steel reinforced concrete, SEA reinforced concrete and SEA reinforced concrete (RC) with pre-tensioning. The results showed that SEA reinforced concrete beams demonstrated strong recentering capability and significant enhancement in crack recovery capacity, in comparison to steel reinforced beams. Furthermore, corresponding finite element models were generated to simulate the experimental observations. Both the experimental observations and finite element computations illustrated the superiority of SEA bars to conventional steel bars in providing RC beam specimens with recentering and crack recovery capabilities.

The value of uniaxial magnetocrystalline anisotropy constant KU in the L10-type Fe48Pd52 single crystal is 2.5×107 erg cm−3 at 4.2 K. The magnetocrystalline anisotropy decreases with increasing temperature. The temperature dependence of KU is described by the l(l+1) power law for a uniaxial system . The longitudinal magnetostrictions in the L10 phase are anisotropic. The value of λ∥a along the a-axis in the L10 phase is about 100×10−6 and larger than that of λ∥100 along the 〈0 0 1〉 direction in the disordered phase and also λ∥c along the c-axis in the L10 phase.

On the basis of our new equilibrium phase diagram, Fe 1− x Ga x ( x =0.24–0.25) single crystals with the A2, B2 and D0 3 structures have been prepared in order to investigate the magnetocrystalline anisotropies and magnetostrictions. The [1 1 0] direction was identified as a hard axis and the anisotropy coefficients were | K 2 |> K 1 >0, 0> K 2 in the A2 and B2 structures. Lowering the symmetry of the atomic arrangement, the magnetostriction of the [1 0 0] direction becomes larger. These results agree with qualitatively the theoretical calculations.

Effects of annealing on the martensitic and magnetic transitions in Ni 51 Ga 27 Fe 22 shape memory alloy were investigated. Curie temperature of the annealed sample decreased with increasing annealing temperature, related to degree of the L2 1 order, S L2 1 . Both martensitic starting M s and the austenitic finishing A f temperatures increased with increasing annealing temperature and showed maxima by annealing at 873 K. The M s and A f seemed to be affected by not only S L2 1 , but also by this magnetic behavior.

We report the results of tensile cyclic loading tests conducted to examine the dependence of constitutive relations for superelastic Cu?Al?Mn alloy rods on loading rates. Recently, Cu?Al?Mn alloy rods with diameters up to 8?mm have been developed by the authors, and it has been demonstrated that these rods have excellent superelastic strains of more than 8%, which is comparable to Ni?Ti alloys and far superior to other Cu-based alloys. No information is available, however, on the rate dependence of constitutive relations for Cu?Al?Mn alloys. In this study, we prepare two Cu?Al?Mn alloy rod specimens, whose lengths and diameters are 150?mm and 8?mm, respectively. Their stress?strain relations are examined under the loading frequencies of 0.001, 0.5, and 1?Hz with constant strain amplitude of 4.5%. It was found from the tests that the maximum stress increase in Cu?Al?Mn alloys due to higher loading rate was less than 5%. Thermo-mechanical analysis predicts that stress increase in Cu?Al?Mn alloys is about 1/4 of that in Ni?Ti alloys, which agrees reasonably well with the experimental observations. Such low stress increase is highly desirable in the design of seismic devices such as dampers and isolators.

The basic concept underlying the alloy design and microstructural control method utilised in developing a new type of β(B2)+ γ (A1) two-phase ductile shape memory alloy in the Ni-Al base systems is briefly reviewed. The characteristic features of the shape memory effect (SME) in the Ni-Al-Fe and Ni-Al-Fe-Mn alloys are reported with particular reference to the transformation and deformation temperatures, the volume fractions of the γ phase, the morphology of the β + γ structure and the effect of cycling. Training by cycling treatment has a significant effect on the degree of shape recovery and pseudo-elasticity in the β + γ two-phase alloys. These duplex β + γ alloys also exhibit a combination of relatively high damping capacity and high yield strength. It is emphasized that these alloys could be expected to fill the need for a new group of shape memory alloys which operate at elevated temperatures over 100°C.

The concentration dependence of magnetic properties in the austenite phase of Ni50Mn50−xInx/2 Sbx/2 Heusler alloys was systematically investigated by magnetization measurements. The Curie temperature for Ni50Mn50−xInx/2Sbx/2 alloys is almost independent of content x. On the other hand, the concentration dependence on magnetic moment shows a concave curve similar to that of Ni50Mn50−xSnx alloys, which have the same number of valence electrons. This tendency suggests that the magnetic moment continues to increase with decreasing content x and reaches that of the metastable ferromagnetic NiMn-B2 phase.

Magnetic properties of the B2 phase in Co50−xNixMn25Al25 alloys were investigated. Spontaneous magnetization Ms measured at 4.2 K increases linearly with increasing x in the region of x ≤ 30 in accordance with following the generalized Slater-Pauling (GSP) line. However, Ms abruptly decreases with increasing x and deviates from the GSP line in the Ni-rich region of x > 30, suggesting a drastic change in the density of states at the Fermi energy. The Curie temperature TC decreases monotonically with increasing x and significantly decreases in the region of x > 30. Antiferromagnetic evidence is clearly observed at x > 45, and the Neel temperature TN increases with increasing x, in reaching the value of the B2 phase in Ni2MnAl.

The concentration dependence of magnetic properties in the austenite phase of NiCoMnIn and NiCoMnSn Heusler alloys was systematically investigated by the magnetization measurements. The TC for Ni(50-x)CoxMn(50-y)Sny alloys linearly increases with increasing the Co content and fixed Sn content. Although showing a concave curve for Ni50Mn(50-y)Sny ternary alloys, the Sn content-dependence of magnetic moment per formula unit changes from the concave curve to a straight line when Co is substituted for Ni. On the other hand, the In content-dependence of the magnetic moment for Ni45Co5Mn(50-y)Iny alloys is perfectly linear as is that in the Ni50Mn(50-y)Iny ternary alloys.

For the Co2Mn(Ga1−xZx) (Z=Si, Ge, and Sn) Heusler alloys, the L21/B2 order-disorder transition temperature TtL21/B2, the Curie temperature TC, and the saturation magnetization Ms were determined. The TtL21/B2 for all the systems linearly increases with increasing x. Although the TtL21/B2 was not determined in the high x region because of melting of alloys, those of Co2MnGe and Co2MnSn could be estimated by extrapolation from the quaternary data. The Ms at 4.2 K and the TC increase with x, and the Ms for all the systems is in good agreement with the Slater Pauling rule.

Spin and orbital magnetic moments of the L21-type Co2FeGa Heusler alloy have been investigated using x-ray magnetic circular dichroism spectra in the soft x-ray region. From the spectra of the L2,3-edge of Co and Fe, the ratios of the orbital magnetic moment to the spin magnetic moment Morb/Mspin are estimated to be 0.06 for Co and 0.02 for Fe, in agreement with the available theoretical values. The orbital magnetic moments of these two elements are small in line with theoretical results, reflecting the high symmetry of the L21-type crystal structure. Furthermore, it has been confirmed that the magnetic moment of Ga is induced in the present alloy.

Both the magnetic and crystallographic microstructures in the ferromagnetic shape memory alloy Ni51Fe22Ga27 were extensively studied by electron holography, electron diffraction, dark-field image observations, and the phenomenological crystallographic theory of martensitic transformations. This study elucidated anomalies that were observed in the magnetic flux pattern before the onset of the martensitic transformation. Furthermore, the observations clarified the relationship between the magnetization vectors and the shape strain directions in the martensite variants that formed a self-accommodation group.