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High-field magnetic measurements were carried out in order to investigate behaviors of field-induced reverse martensitic transformation and kinetic arrest of NiCoMnSn metamagnetic shape memory alloy. In the thermomagnetization curves, it was confirmed that the reverse martensitic transformation temperature decreases 67 K by applying magnetic field of 5 T, while in the magnetic field cooling process under 5 T, martensitic transformation does not occur down to low temperatures. Equilibrium magnetic field, defined from the critical magnetic fields of the metamagnetic evidence in the magnetization curves, exhibits almost constant below about 100 K, suggesting that the entropy change becomes zero, which is considered to cause kinetic arrest behavior.

Magnetic properties and martensitic transformation response of the Ni43Co7Mn39Sn11 metamagnetic shape memory alloy compacts fabricated by pressureless sintering were investigated. The porous specimens sintered at 1173 K for 48 h show drastic change of electrical resistivity and magnetization due to martensitic transformation, and the features of magnetic-field-induced martensitic transformation behavior are almost the same as those in bulk specimens. In the porous specimens, the large metamagnetic shape recovery ratio over 40% was observed at 320 K with the application of 8 T magnetic field.

Mechanical and shape memory properties of Ni43Co7Mn39Sn11 metamagnetic shape memory sintering compacts, fabricated by pressureless sintering, were investigated. With sintering time the porosity drastically decreases and the ductility is significantly enhanced compared to the samples obtained by conventional induction melting. Moreover, the fracture strain in the specimen sintered at 1173 K for 144 h is almost the same as that in the high density sintering compacts by spark plasma sintering. Interestingly, the shape memory effect decreases with decreasing porosity.

The phase equilibria at 900 °C and B2/L21 order-disorder transition in the Ni-Mn-Ga ternary system were investigated by analyzing the equilibrated alloys and diffusion couples using a combination of techniques. It was confirmed that a bcc single phase region exists in a wide composition range at 900 °C, and the critical temperatures of B2/L21 order-disorder transition were determined in Ni-50 at.% section, which exhibits a maximal ordering transition temperature of 796 at Mn content of 25 at.%. The obtained results will be helpful for the preparation and annealing of Ni-Mn-Ga alloys in the specific temperature.

We present the results of the quasi-static cyclic tensile tests of Cu–Al–Mn shape memory alloy (SMA) bars of 4 and 8 mm diameters to examine their superelasticity and other mechanical properties closely related to seismic applications. The present Cu–Al–Mn SMA bars have achieved the recovery strains of over 8% and the fracture strains of over 17%. Low-cycle fatigue was observed in neither of the bars. The mechanical properties obtained from the test, along with the lower material cost and higher machinability than Ni–Ti SMAs, demonstrate the high potential of the present Cu–Al–Mn SMA bars to be used in seismic applications. Copyright © 2010 John Wiley & Sons, Ltd.

This work first deals with the effect of Nb addition on the liquid phase separation in the Cu–Co system, which displays a metastable liquid miscibility gap. The isothermal sections at 800, 900, 1000, 1100, and 1200 °C in the Cu–Co–Nb system have been experimentally determined by optical microscopy, electron probe microanalysis, and x-ray diffraction on the equilibrated alloys, and the phase equilibria in the Cu–Co–Nb ternary system were thermodynamically assessed by using CALPHAD (Calculation of Phase Diagrams) method on the basis of the presently determined experimental data. Nb additions can stabilize the metastable liquid phase separation in the Cu–Co binary system and significantly increase its critical temperature. The solidified Cu–Co–Nb alloys appearing on the top-bottom separated microstructural morphology under low cooling rate while forming core-type macrostructural morphology under high cooling rate have been confirmed.

At room temperature, Co 41 Ni 32 Al 27 single-variant ferromagnetic shape memory alloy with a uniaxial magnetic anisotropy constant of –2.0 × 10 6 erg cm –3 exhibits a large magnetic-field-induced strain of 3.3% under a static compressive stress of about 10 MPa applied along the hard magnetization direction of the c -axis ( c / a > 1). Compared with data for other alloys, it becomes clear that a small change in twinning stress in the stress–strain curve is necessary for a large strain.

Heat-induced and isothermal martensitic transformations from kinetically arrested parent phase in Ni 45 Co 5 Mn 36.7 In 13.3 metamagnetic shape memory alloy were investigated by magnetization measurements. A drastic drop of magnetization due to martensitic transformation during heating was observed. The isothermal martensitic transformation was confirmed to appear for some combinations of temperature and field. Incubation time for the transformation strongly depended on the holding condition, and the specimen held in conditions near the martensitic start ( M s ) line determined by magnetization measurements showed a shorter incubation time.

Site occupancies of Co, Y (Y = Ti, V, Cr, Mn and Fe) and Ga atoms for the L21 phase in Co2YGa alloys annealed at 773 K were precisely investigated by powder neutron diffraction measurement. While Co atoms in all the five alloys almost perfectly occupy the x (2a) site, the occupancy of the z (4b) site by Ga atoms depends on the kind of Y atom, and it decreases with increasing number of valence electrons except for Co2CrGa alloy. Degrees of long-range order on the z site occupancy of Ga atoms experimentally determined for all the alloys are in good agreement with those thermodynamically estimated from their order–disorder transition temperatures using the Bragg–Williams–Gorsky approximation.

A materials design tool for developing Pb-free soldering alloys in electronic package was developed based on comprehensive experimental data of phase equilibria and thermodynamic properties data accumulated with the CALPHAD (calculation of phase diagrams) method and contains 10 elements, namely, Ag, Au, Bi, Cu, In, Ni, Sb, Sn, Zn and Pb. It can handle the calculation of phase diagrams in all combinations of these elements and all composition ranges. In addition, based on this tool, the liquidus, solidus, phase fractions and constitutions, equilibrium and non-equilibrium solidification behavior, surface tension and viscosity of liquid, diffusion reactions and microstructural evolution, etc. can be predicted. Typical examples of the calculation and application of this tool are presented. The design tool is expected to be a powerful tool for the development of Pb-free solders, as well as for promoting the understanding of the interfacial phenomena between Cu substrate and Pb-free solders in electronic packaging technology.

The phase equilibria at 200 °C, 250 °C, 300 °C, and 400 °C and the phase transformation of the Sn-Au-Bi system were investigated by using the electron probe micro-analyzer (EPMA) and differential scanning calorimeter (DSC), respectively. It is found that there is a new ternary intermetallic compound with a possible AuSn structure (called the ϕ phase in the present work), which has a limited solubility of Au in the Au-rich portion, and the ϕ phase decomposes peritectically at about 313 °C. Based on the experimental data reported in the previous papers and new experimental data determined by the present work, thermodynamic assessments of the Sn-Au-Bi system were carried out by the calculation of phase diagrams (CALPHAD) method. The thermodynamic parameters for describing the Gibbs free energy of each phase were optimized, and reasonable agreement between the calculated results and experimental data was obtained in the Sn-Au-Bi ternary system.

The phase diagrams and thermodynamic properties in the Ag–Er and Er–Y binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, and hcp phases were described by the subregular solution model with the Redlich–Kister equation, and those of intermetallic compounds (Ag2Er and AgEr phases) were treated as stoichiometric compounds, and Ag51Er14 phase was modeled by the sublattice model in the Ag–Er binary system. The thermodynamic parameters of the Ag–Er and Er–Y binary systems were obtained, and an agreement between the calculated results and experimental data was obtained for each binary system.

The order–disorder transformation and the magnetic properties of Heusler-type Ni50Mn50−xInx ternary alloys were investigated. The B2/L21 order–disorder transformation temperatures are detected at about 800–1100 K. In the alloys with the L21 structure, while the spontaneous magnetization at 4.2 K monotonically decreases with increasing x, the Curie temperature is almost constant with x ⩽ 25 and decreases linearly with x > 25. This unique behavior is qualitatively explained by the concept of local magnetic moment of Mn atoms.

Interdiffusion coefficients of the A2- and B2-type Fe–Al intermetallics were determined at 1073 and 1273 K from solid–solid diffusion couples by using the modified Boltzmann–Matano method. The atomic mobilities for the two phases were reassessed in terms of phenomenological treatment, which permits prediction of interesting diffusion details, such as the effect of chemical ordering on diffusion, the Al tracer diffusivity and the Kirkendall shift.

Magnetic properties and martensitic transformation behaviors of NiCoMnAl metamagnetic shape memory alloys were investigated. The kinetic arrest phenomenon was observed at about 40 K during thermomagnetization measurements. At temperatures ranging from 4.2 to 200 K, magnetic field-induced reverse transformation was confirmed by a pulse magnetometer with a magnetic field up to 45 T. By plotting the equilibrium magnetic fields against the measured temperature, the transformation entropy change was calculated by using the Clausius-Clapeyron equation. The transformation entropy change was found to become zero below 40 K, which can explain the appearance of the kinetic arrest phenomenon.

Shape memory response of the polycrystalline Ni 40 Co 10 Mn 33 Al 17 alloy were investigated. In the isobaric thermal cycling experiments, the measured transformation strain levels increased with increasing stress reaching about 3.6% under 200 MPa. The slope of the stress vs. transformation temperature diagram, constructed using the data from these experiments, almost coincided with the predicted one obtained using the Clausius-Clapeyron equation, and experimental entropy data and transformation strain. Perfect pseudoelasticity was observed up to 405 k during compressive straining up to 2.5%.

Mechanical properties of Fe-20Mn-(10-14)Al-(0-1.8)C (mass%) quaternary and Fe-20Mn-(10-14)Al-(0.75-1.8)C-5Cr (mass%) quinary alloys were investigated by hardness, cold-workability and tensile tests at room temperature. The γ(fcc) alloys in both quaternary and quinary systems with a low density of less than 7.0 g/cm 3 showed an excellent ductility and their hardness and tensile strength increased with increasing Al and C contents. The γ+α(bcc) duplex alloys also exhibited a high tensile strength by controlling the α volume fraction. TEM observation confirmed that high hardness and tensile strength of the alloys with high Al and C contents are caused by the precipitation of nano-size κ-carbide with perovskite structure during cooling from the annealing temperature. Fe-20Mn-11Al-1.8C-5Cr alloy with a density of 6.51 g/cm 3 showed a high specific strength of more than 180 MPa · cm 3 /g with a good tensile elongation of 40 %. The present Fe-20Mn-Al-C(-5Cr) alloys showed a higher specific strength than conventional steels.

Oxidation resistance and tribological properties of SHS-produced chromium sulfide have been explored. The material was oxidized up to 5 to 7 μm thick from its surface upon heat treatment at 1000°C for a short time. It also exhibited a unique compositional change in sulfur and chromium at the interface between matrix and oxide layer formed during heat treatment. Meanwhile, the synthesized material showed the coefficient of kinetic friction of below 0.18, which is an acceptable value for a solid lubricant. Although the friction coefficient of CrS was initially low, it was found to grow upon high-temperature oxidation of the CrS surface. This fluctuation in the tribological property seems to depend on both the crystal structures of chromium sulfide and chromium oxide and of the interface between the oxide and matrix.

Phase equilibria in the Co-rich Co–Al–W ternary system were determined with a unique diffusion-couple technique in which Co–27Al and Co–15W binary alloys (at. %) were first coupled for interdiffusion and then heat-treated for precipitation. After a diffusion process at 1300 °C for 20 h, concentration gradients of Al and W were formed in the γ-Co(A1) matrix in the vicinity of the coupled interface. After a heat treatment at 900 °C for 500 h the γ′-Co3(Al,W)(L12) phase was formed with a coarsened shape in contact with the γ, CoAl(B2) and Co3W(D019) phases. Additionally, it appeared with a submicron cuboidal shape within the γ matrix. After 2000 h, however, the coarsened γ′ phase became infrequent and the three phases of γ, CoAl and Co3W came into frequent contact with each other. These results clearly demonstrate that the γ′ phase is metastable and the three phases of γ, CoAl and Co3W are thermodynamically in equilibrium at 900 °C in the Co–Al–W ternary system.

The magnetic properties of the parent and martensite phases of the Ni2Mn1+xSn1-x and Ni2Mn1+xIn1-x ternary alloys and the magnetic field-induced shape memory effect obtained in NiCoMnIn alloys are reviewed, and our recent work on powder metallurgy performed for NiCoMnSn alloys is also introduced. The concentration dependence of the total magnetic moment for the parent phase in the NiMnSn alloys is very different from that in the NiMnIn alloys, and the magnetic properties of the martensite phase with low magnetization in both NiMnSn and NiMnIn alloys has been confirmed by Mössbauer examination as being paramagnetic, but not antiferromagnetic. The ductility of NiCoMnSn alloys is drastically improved by powder metallurgy using the spark plasma sintering technique, and a certain degree of metamagnetic shape memory effect has been confirmed.

The pressure effect on the Curie temperature T C of Heusler alloys Ni 2 Mn 1+ x Sn 1− x (0 ≤ x ≤ 0.28) has been investigated by measuring the temperature dependence of initial permeability at various pressures up to 10 kbar. The pressure derivative of T C , d T C /d p , of Ni 2 MnSn is found to be +0.5 K/kbar. The values of d T C /d p for Ni 2 Mn 1+ x Sn 1− x (0 ≤ x ≤ 0.28) alloys decrease with increasing the concentration x . The pressure effect on T C for Ni 2 Mn 1+ x Sn 1− x (0 ≤ x ≤ 0.28) alloys is discussed qualitatively on the basis of the interatomic dependence of the exchange interactions.

The effects of ageing at 473–573 K on the hardness, microstructure and thermoelastic martensitic transformation in Cu–Al–Mn-based shape memory alloys were investigated. It was found that hardness was dramatically increased by ageing due to the formation of fine bainitic plates and that the volume fraction of the bainite phase with ageing time can be described by the Austin–Rickett equation. The martensitic transformation temperatures decreased with the formation of bainite plates, mainly due to the composition change of the β-matrix. Moreover, the growth of thermally induced martensite plates was disturbed by the existence of bainite plates. Consequently, the transformation intervals ( M s – M f and A f – A s ) and transformation hystereses ( A f – M s and A s – M f ) increased with the progress of bainitic transformation.

Phase equilibria and stabilities of intermetallic phases appearing in the Co-rich portion of the Co-W-Ga ternary alloys were investigated and isothermal section diagrams at 1200, 1100, 1000, and 900 °C were determined. A fine cuboidal phase with an L12 structure was observed at 900 and 800 °C, where the composition of the new ternary compound obtained by aging at 900 °C for the Co-7.4W-12.0Ga alloy was Co-11.2W-11.4Ga (at.%). It was confirmed that this compound is metastable at 900 °C but is more stable at 800 °C. These results mean that the thermodynamic stability of the metastable Co3W L12 phase, especially in the low temperature region, increases by the addition of Ga.

Magnetization and initial permeability measurements were done on the magnetic shape memory alloys Ni2Mn1.48-xFexSn0.52 (0 ⩽ x ⩽ 0.20). The Curie temperature TC in the austenite phase increases slightly with increasing x. Similarly, the Curie temperature T′C in the martensite phase increases with increasing x. The martensitic transition starting temperature Ms decreases steeply with increasing x. The paramagnetic state of the martensite phase collapses in the Fe-rich alloys.

The phase diagrams and thermodynamic properties in the Ag–Tb and Ag–Ho binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc and hcp phases were described by the substitution solution model with excess energy expressed by Redlich–Kister polynomial, and those of intermetallic compounds (Ag2Tb, AgTb, Ag2Ho and AgHo phases) were treated as stoichiometric compounds, and Ag51 Tb14 and Ag51 Ho14 phases were modeled by the sublattice model in these two binary systems. The thermodynamic parameters of each phase in the Ag–Tb and Ag–Ho binary systems were obtained, and an agreement between the calculated results and experimental data was obtained in each binary system.

The mechanical properties of several B-free and B-doped Co–Al–W superalloys with different volume fractions of the Co3(Al,W)-γ′ phase were examined by mechanical tests at various temperatures up to 980 °C. Although grain boundary fracture occurred in the B-free alloys, the addition of a small amount of B drastically improved the ductility. It was also confirmed that the positive temperature dependence of strength was strongly affected not only by the volume fraction of the γ′ phase, but also by the addition of B.

Martensitic transformation and magnetic properties were investigated for Ni43Co7Mn39Sn11 polycrystalline specimens obtained using the spark plasma sintering method. The microstructure of the specimen sintered at 1173 K for 15 min showed only a small number of pores, and the specimen’s ductility was significantly higher than that of alloys fabricated by conventional induction melting. The martensitic and magnetic properties of the sintered specimen were basically similar to those of conventional bulk alloys. The metamagnetic shape memory effect, i.e. magnetic field-induced shape recovery, was confirmed by the magnetic field of 8 T.

National Natural Science Foundation of China [50425101, 50571084, 50771087, 50771088]; Ministry of Science and Technology [2009DFA52170]; Ministry of Education, P.R. China [20050384003, 707037]; Grant-in-Aid Core Research for Evolutional Science, and Tech

The National Natural Science Foundation of China [50425101, 50571084]; The Ministry of Science and Technology of China [2004CCA04200]; The Ministry of Education of China [20050384003, 105100, 707037]; Grant-Aid Core Research for Evolution Science and Tech

The phase equilibria at 300, 400, 500, and 600 °C in the Ag–Bi–Ni system and 300, 400, and 500 °C in the Cu–Bi–Ni system were experimentally determined by metallography and electron probe microanalysis on equilibrated alloys and diffusion couples. Differential scanning calorimetry was used to measure the temperatures of phase transformations. All the experimental results show that the solubilities of the ternary elements of the binary intermetallic compounds in the Ag–Bi–Ni system are limited. However, the binary intermetallic compounds have some solubilities of the ternary elements in the Cu–Bi–Ni system. No ternary intermetallic compound was found in the Ag–Bi–Ni and Cu–Bi–Ni systems. On the basis of the determined results, the phase equilibria in the Ag–Bi–Ni and Cu–Bi–Ni systems were thermodynamically assessed, and reasonable agreement between the calculated results and experimental data was obtained.

National Natural Science Foundation of China [50425101, 50771088]; Ministry of Education, PR China [707037]; Core Research for Evolutional Science and Technology ( CREST); Japan Science and Technology Agency (JST)

National Natural Science Foundation of China [50425101, 50571084]; Ministry of Education, PR China [20050384003, 707037]; Core Research for Evolutional Science, and Technology (CREST); Japan Science and Technology Agency (JST)

Phase equilibria in the Cu–Cr–Nb and Cu–Cr–Co systems were, respectively, determined by metallography, X-ray diffraction (XRD) and scanning electron microscopy–energy dispersive X-ray (SEM–EDX) techniques. The thermodynamic assessments of the Cu–Cr–Nb and Cu–Cr–Co systems were carried out by using CALPHAD (CALculation of PHAse Diagrams) method on the basis of the experimental data measured by the present and previous works. The Gibbs free energies of the liquid and solid solution phases were described by the subregular solution model, and those of intermetallic compounds were described by the sublattice model. A consistent set of the thermodynamic parameters has been obtained, and the evaluated thermodynamic parameters lead to a better fit between calculated results and experimental data in both the Cu–Cr–Nb and Cu–Cr–Co systems.

X-ray powder diffraction and magnetization measurements were done on the magnetic shape memory alloys Ni2Mn1+xIn1−x. On the basis of the results, the magnetic phase diagram was determined for Ni2Mn1+xIn1−x alloys. Magnetization measurements make clear that the excess Mn atoms, which substitute for In sites, are coupled ferromagnetically to the ferromagnetic manganese sublattices. A magnetic phase diagram of Ni2Mn1+xIn1−x alloys is discussed qualitatively on the basis of the interatomic dependence of the exchange interactions.

Magnetic change due to the martensitic transformation induced by high magnetic fields up to 18 T was investigated in the Ni50Mn34In16 metamagnetic shape memory alloy. Kinetic arrest of the martensitic transformation was observed and the martensitic transformation no longer proceeded at temperatures below around 100 K. The transformation entropy change between the martensite phase and parent phase evaluated from the magnetization curves showed an unusual behavior, changing from positive to negative at about 80 K.

Three types of inexpensive Pb-free solder joints, namely Zn-based and Bi-based solders, and a CuSn alloy were studied for application to the high-temperature operation of wide band-gap power semiconductor devices using GaN or SiC. Zn–Al solder sheets, whose melting point is 380°C were prepared, and then surface oxides were removed by RF plasma etching. Subsequently, Cu thin films were deposited by the DC sputtering method on the solder sheet. After that, joint samples were fabricated using a conventional electrical furnace with H2/N2 gas flow. That the joints were sufficiently dense was confirmed by scanning acoustic microscope. The wettability of the solder was improved due to contact between the pure Zn–Al solder without oxide and the Ni surface of the substrate, and the chemical reaction between the Zn–Al solder and the deposited Cu thin film. Bi with CuAlMn particle solders, whose melting point is 270°C, were fabricated and it was found that the solder has almost double the tensile strength of pure Bi. Excellent wettability was observed with the Ni or Pd thin film deposited on the Cu substrate. It was found that deposited Ni or Pd was not observed in the interface between the substrates after the joint samples were fabricated. CuSn alloy joints were fabricated using Sn thin films deposited and annealed on Cu substrates. The temperature during the annealing was kept at approximately 350°C; therefore, only the Sn film was melted and some chemical reaction occurred between the liquid Sn and solid Cu. Then, Cu3Sn alloy, whose melting point is 640°C, appeared in the joint and the composition was confirmed by X-ray diffraction analysis. Furthermore, it was found that the CuSn alloy is harder than Cu as measured by nano indentation analysis. In addition, the joints showed excellent thermal cycle reliability.Finally, the properties of these joints are summarized.

The phase equilibria in the FeS–XS and MnS–XS (X: Ti, Nb and V) pseudo-binary systems were investigated by using an X-ray diffraction and electron probe micro analyzer. In the FeS–TiS and FeS–VS systems, a mono-sulfide with the NiAs structure form a complete solid solution, while two-phase separation of the mono-sulfide with the NiAs structure is observed in the FeS–NbS system. In all MnS–XS systems, two-phase region of a Mn-rich mono-sulfide and X-rich mono-sulfide exists widely. Solubility of each elements in the Mn-rich mono-sulfide and X-rich mono-sulfide is small, except that of Mn in Nb-rich mono-sulfide.

Low-frequency elastic modulus, internal friction, tensile stress-strain loops, and thermally-induced strain recovery of single-crystal fibers obtained by pulling-down method from the melts of NiFeGaCo alloys were studied. A minimum of the elastic modulus and the maximum peak of the internal friction were obtained at the martensitic transition temperature. A large super-elastic strain of about 10% was obtained in the fiber of the Ni(49)Fe(18)Ga(27)Co(6) alloy. Thermodynamic estimation by the Clausius-Clapeyron equation was consistent with the experimental results.

Solubility of sulfur in Fe–V and Fe–Nb alloys was experimentally determined using a diffusion couple technique. Solubility product of VS and NbS in ferrite (α) and austenite (γ) phases were determined as log(mass%V)(mass%S)α=4.76−10100/T, log(mass%V)(mass%S)γ=4.90−11000/T and log(mass%Nb)(mass%S)γ=4.70−10500/T in the temperature range from 1523 to 1573 K. A thermodynamic analysis was also carried out to evaluate the formation energy of VS and NbS. The estimated formation energy of VS and NbS are ΔGVSsulfide=−263100+61.0T (J/mol) and ΔGNbSsulfide=−260800+68.4T (J/mol), respectively.

Phase equilibria between the α (A2), α' (B2) and γ (A1 ) phases in the Fe-Rh binary system were investigated using electron probe micro-analysis (EPMA) and differential scanning calorimetry (DSC) techniques. The A2/B2 order-disorder transformation temperature was also examined by a transmission electron microscope (TEM) observations and high-temperature X-ray diffraction (HTXRD). It was confirmed that while the transition temperature from the α (A2) phase to the γ (A1 ) phase decreases with increasing Rh content up to about 20 at% Rh, the b.c.c. region is stabilized by further Rh addition in the composition range between about 20 and 50 at% Rh, and then again the stability of b.c.c. phase decreases in the composition region over 50 at% Rh. It was also shown by TEM observation and HTXRD examination that the compositions of the phase boundary of the A2/B2 ordering at 500°C and 600°C were determined to be 16.5 and 19.1 at% Rh, respectively. On the basis of those experimental results, a thermodynamic analysis was carried out. The results of the thermodynamic calculation suggest that the anomalous behavior of the stability of the b.c.c. phase is caused by the A2/B2 ordering.

The phase stability and magnetic properties of Ni2Mn(GaxAl1−x) alloys were studied by differential scanning calorimetric and magnetometric measurements, and X-ray diffraction and transmission electronic microscopic observations. The order–disorder transition temperature from the B2 to the L21 phase, T t B 2 / L 2 1 , linearly increases with increasing x and the magnetic properties depend on the annealing conditions. Especially in the Ni2Mn(Ga0.5Al0.5) alloy, the condition of the atomic order can be varied from a B2 to an L21 structure by the annealing temperature. The magnetic property of the fully ordered L21 phase is ferromagnetic with a Curie temperature TC of about 380 K, while that in the B2 phase is antiferromagnetic with the Neel temperature TN of about 300 K.

National Natural Science Foundation of China [50425101, 50571084, 50771088]; Ministry of Science and Technology of China [2004CCA04200]; Ministry of Education of China [20050384003, 105100]; Fujian International Cooperation Foundation; Fujian Natural Scie

Phase equilibria among the α (A1), α′ (L1 2 ), β (B2), δ (Ni 5 Ga 3 ) and ɛ (Ni 13 Ga 9 ) phases at elevated temperatures and the existing composition region of the martensite phase at room temperature in the Ni–Co side of the Ni–Co–Ga system were examined by electron probe microanalysis (EPMA) using diffusion triples which were fabricated by two-step diffusion coupling. It was confirmed that single-phase regions of the α, α′ and β phases at 700 and 1000 °C exist in a wide composition range parallel to Ni–Co section and that the existing region of the martensite phase at room temperature is also located over a wide range in the β phase along the β + α (or α′) two-phase region.

The order–disorder phase transition temperature from L 2 1 to B 2 phase T t L 2 1 / B 2 , the saturation magnetization M s and the Curie temperature T C were investigated in Co 2 (Ti 1− x Fe x )Ga. It was confirmed that T t L 2 1 / B 2 for 0.8 ⩽ x ⩽ 1.0 almost linearly decreases with increasing x , and M s follows the generalized Slater–Pauling line in the middle region of x . T C also increases with increasing x , exhibiting an upward convexity. It is concluded that a relatively high T t L 2 1 / B 2 , a high T C and a low M s can be obtained in the present alloys.

The phase equilibria, A2/B2 and B2/L2 1 (or D0 3 ) order–disorder transitions and martensitic transformation on the Ni–Fe side of the Ni–Fe–Ga system were examined by electron probe microanalysis (EPMA) and differential scanning calorimetric (DSC) measurement. The equilibrium compositions of interrelations mainly among the α (A2), β (B2), β′ (L2 1 or D0 3 ), γ (A1) and γ′ (L1 2 ) phases were determined using diffusion triples which were fabricated by two-step diffusion coupling. It was confirmed that a bcc single-phase region composed of α, β and β′ at 850–1000 °C exists in a wide composition range and that the critical temperature of the B2/L2 1 order–disorder transformation in the Fe 3 Ga–Ni 3 Ga pseudo-binary section gradually increases with increasing Ni content. The existing composition region of the martensite phase at room temperature was also determined by the diffusion triple method.

The Zn-Al(-Cu) eutectic alloys (melting point 381°C) are candidates for use as Pb-free high-temperature solders as a substitute for Pb-based solders, which are suitable for severe working environments such as the engine room of hybrid vehicles equipped with an inverter system as well as a heat engine. In this study, the interfacial reaction between Zn-Al(-Cu) alloys and the Ni substrate during soldering, aging, and thermal cycling was investigated. Semiconductor chips and Ni substrates were soldered with Zn-Al(-Cu) alloys at various temperatures under a nitrogen atmosphere. The soldered assemblies were then heat-treated at 200°C and 300°C to examine the microstructural evolution at the soldered interface. The effect of severe thermal cycles between −40°C and 250°C in air on the microstructure and fracture behavior at the solder joint was investigated. Even after a 1000-cycle test, the thickness of the Al3Ni2 layer formed at the interface between the Zn-Al-based solder and the Ni substrate, which is responsible for the damage of the soldered assemblies, was quite small.

Polycrystalline Cu–Al–Mn shape memory alloys (SMAs) with a low degree of order of the β (L21) phase show excellent ductility and exhibit shape memory (SM) properties such as superelasticity, the one way memory effect and the two way memory effect based on martensitic transformation. These SM properties can be greatly enhanced by controlling microstructural factors such as grain size and texture by thermomechanical treatments. In the present paper, the SM properties of ductile Cu–Al–Mn based SMAs and microstructure control to obtain excellent SM characteristics are reviewed. Furthermore, an example of the application of Cu–Al–Mn based SMAs to a guidewire for medical use is also presented.

In order to develop the thermodynamic database of phase equilibria in the Mg–Zn–Re (Re: rare earth element) base alloys, the thermodynamic assessments of the Ce–Zn and Pr–Zn systems were carried out by using the calculation of phase diagrams (CALPHAD) method on the basis of the experimental data including thermodynamic properties and phase equilibria. Based on the available experimental data, Gibbs free energies of the solution phases (liquid, bcc, fcc, hcp and dhcp) were modeled by the subregular solution model with the Redlich–Kister formula, and those of the intermetallic compounds were described by the sublattice model. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Ce–Zn and Pr–Zn binary systems. An agreement between the present calculated results and experimental data is obtained.

The thermodynamic assessments of the Co–Th and Fe–Th binary systems were carried out by using the calculation of phase diagrams (CALPHAD) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, and hcp phases were described by subregular solution model with the Redlich–Kister equation, and those of the intermetallic compounds (Co17Th2 ,C o 5Th, Co7Th2, CoTh, Co3Th7 ,F e 17Th2 ,F e 5Th, Fe7Th2 ,F e 3Th and Fe3Th7) in these two binary systems were described by sublattice model. The thermodynamic parameters of the Co–Th and Fe–Th binary systems were optimized for reproducing the experimental data, respectively, and an agreement between the calculated results and experimental data was obtained in each binary system. © 2007 Elsevier B.V. All rights reserved.