The mechanism of thermoelastic fcc-fct martensite transformation of Fe–Pd alloys containing about 30 at%Pd was studied by optical and transmission electron microscopy. It was found that the fcc-fct transformation was not accompanied with internal twins in the beginning of the transformation, but they were introduced during the growth process of the fct martensite in which the degree of tetragonality increased. In the fcc austenite phase, the remarkable tweed contrast consisting of {011}/⟨0\bar11⟩ striations and accompanying diffuse streaks perpendicular to them was observed, and lamellae appeared along the tweed contrast with cooling under the in situ electron microscope observation. The lamellae were identified not with the fct martensite variant plates but with thin {011} internal twins of the fct martensite, and the tweed contrast disappeared in the inside of lamellae. From the microscopical and diffraction analysis, it was found that the tweed contrast is caused by the static displacement of R=δ{011}⁄⟨0\bar11⟩, and the origin of the static displacement is the formation of the very thin platelets of martensite nuclei. At the transformation temperature, the enhancement and extension of the tweed contrast occurred leading to the fct martensite phase. Taking account of the results that the tweed contrast persistently remained in the fct martensite except in the inside of internal twins, the variant mosaic structure model was proposed and the mechanism of the fcc-fct thermoelastic martensite transformation was successfully explained.

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Crystal structure, composition and morphology of the precipitate in an aged Ti-51 at%Ni shape memory alloy have been examined by means of high voltage and high resolution analytical electron microscopy. As a result, the following have been clarified. The precipitate possesses a rhombohedral structure with a=0.670 nm and α=113.8° and contains 14 atoms in the unit cell. The compositional ratio in the unit cell is deduced to be Ni₄Ti₃, from consideration of space group. The composition is well consistent with Ni₅₆Ti₄₄ experimentally obtained from energy dispersive X-ray spectroscopy, within experimental error. The crystal structure is a slight modification of the B2 structure of matrix. The calculated intensity distribution in reciprocal space based on the structure model is in qualitative agreement with the observed one. Lenticular morphology of the precipitate, internal {\bar15\bar4}_R twins and antiphase domains are successfully explained by the structure model. On the basis of this knowledge, a relation between the existence of such precipitates and the appearance of all-round shape memory effect is briefly discussed.

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Structures of Ti–Al–V alloys have been examined by means of electron probe microanalysis and X-ray diffractometry after being annealed for 2.68 Ms at 1073 K or for 691 ks at 1273 K.
Two three-phase equilibriums, Al₈V₅+(V, Ti)Al₃+(V) and Ti₃Al+(β−Ti)+TiAl, have been found, and isothermal diagrams at 1073 K and 1273 K have been reconstructed.
The titanium content in Al₈V₅ phase is about 5 mass% at 1273 K and 1 mass% at 1073 K. In the TiAl compound which contains vanadium up to the solubility limit, the axial ratio c/a varies from 1.012 to 1.050 with increasing aluminium content.

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A herringbone structure observed in an as arc-melted specimen was investigated using XRD, TEM and surface relief study. The specimen was cooled on a water cooled copper hearth and the grain size was approximately 1 mm. The results confirmed the crystal structure to be tetragonal (a_t=0.5100 and c_t=0.5166 nm, c⁄a=1.0129). The orientation relation among the different variants of the tetragonal lattice and their arrangement in the herring bone structure were determined; the structure was shown to be suited for accommodation to the cubic (fluorite structure) to tetragonal transformation strain. Surface relief associated with the transformation was also observed and correlated to the transformation strain. From these results, the transformation was suggested to be of diffusionless type (martensitic).

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The delayed fracture of an ultrahigh strength maraging steel in hydrogen gas was studied with notch tensile specimens at room temperature. It was shown that the delayed fracture behaviors in hydrogen gas were affected significantly by the environmental conditions during loading. When the specimens were loaded in hydrogen gas, the delayed fracture strength was extremely low. When they were loaded under vacuum and then exposed to hydrogen gas environment, the delayed fracture strength was considerably higher than that of the specimens loaded in hydrogen gas. This difference in the degree of embrittlement between them was able to be explained by the strong dependence of the hydrogen absorption at the fresh surface, that was produced by plastic deformation, on the environmental conditions during loading, that is, the delayed fracture was probably controlled by the hydrogen absorption. The delayed fracture strength evaluated by loading in hydrogen gas was approximately equal to the notch tensile strength obtained by the slow strain rate technique in hydrogen gas at pressures of both 6.67 kPa and 66.7 kPa, and both strength values in 6.67 kPa hydrogen gas were also equal to those in 66.7 kPa hydrogen gas. These strength values were estimated to be the lower critical stress below which the fracture of the notch tensile specimens did not occur in the hydrogen gas environment used in this study. This lower critical stress was discussed in view of the start of the plastic deformation at the notch root of the specimens.

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The effect of θ precipitates and deformation at elevated temperatures on the shear band formation has been investigated in rolled single crystals of an Al-2%Cu alloy based on observations of slip bands and dislocation structures. Irrespective of heat treatments to give either a nominal solid solution or θ precipitates, shear bands were not formed in (011)[\bar100] crystals but in (211)[\bar111] crystals during rolling at room temperature. Increase in the temperature up to 473 K resulted in rather homogeneous slip and developed no shear bands even in the (211)[\bar111] crystals. A simple correlation between the shear band formation and dislocation structures was found; the shear bands occurred in the crystals in which aligned micro-bands (layered dislocation walls) evolved.

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Many researches on ceramics have been reported, but brittleness is a key problem to be overcome. However, no generalized method on impact test of ceramics has been reported.
The total absorbed energy evaluated from the Charpy impact test for brittle materials includes largely the energy absorbed by the machine and the kinetic one of the broken specimen, in addition to the real fracture one of the specimen. These energies, therefore, must be exactly analyzed and then the real fracture one is to be evaluated.
In this study, the absorbed energy of partially stabilized zirconia (PSZ) and SiC is analyzed in the instrumented Charpy impact test and in the static three-point bend test. Moreover, the influence of stress-induced phase transformation on the toughness in PSZ is investigated.
As a result, it is shown that the real fracture energy of PSZ is 57–59% of the total absorbed one and that the one of SiC is 38–56%. It is also shown that the amount of stress-induced phase transformation in the impact test is more than the one in the static three-point bend test. Furthermore, it is pointed out that a singularly oscillated loading is found in the impact test of PSZ, which is due probably to the co-working effect between the inertia effect and the stress-induced phase transformation during the dynamic fracture.

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The logarithmic decrement δ, the rigidity modulus G and the tensile strength σ_t have been studied on Al–Si alloys containing 0–15%Si when heat-treated or subsequently cold-worked. Measurements of δ and G were carried out at a frequency of 1 Hz by an inverted torsion pendulum method, and the σ_t was measured using an Instron-type testing machine.
The δ values of the heat-treated alloys are very small and increase with Si concentration. The δ in the furnace-cooled state is larger than that in the water-quenched state. With further cold working, the values exhibit an abrupt increase with increasing degree of working.
The G and σ_t values of the alloys in the heat-treated state increase with Si concentration. The G and σ_t show large values when furnace-cooled and water-quenched, respectively. With further cold working, the G decreases and the σ_t increases.

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