A study was made of the morphology and the orientation relationship of γ formed from Fe–Ni martensite during annealing below the As (austenite start) temperature where the diffusional process is considered to play a dominant role in the γ formation. Rod-like γ particles were precipitated within the matrix of recrystallized grains when martensite of 10%Ni content was severely cold worked before annealing. From martensite of higher Ni content, small spherical γ grains were formed prior to the recrystallization of the matrix, whereas the γ phase appeared almost entirely at the boundaries of recrystallized grains in a lower Ni alloy. From undeformed martensite, needle-like γ was formed along lath boundaries. Both γ rods and γ needles were found to have the Kurdjumov-Sachs orientation relationship with the surrounding matrix.
While γ rods were equally present with their long axes parallel to every [111]_α direction of the matrix, γ needles precipitated in a block of martensite laths were found to have almost the same orientation, for which internal strain created by the forward transformation seems to be responsible. It was also found that γ rods were transformed into martensite crystals having nearly the same orientation as the matrix of the grain from which they appeared.

View full abstract

The measurements of thermodynamic quantities for tin-zinc and indium-antimony binary alloys and for the cadmium chloride-lead chloride and lead chloride-zinc chloride binary mixtures were carried out by quantitative thermal analysis of the heating process. A double adiabatic wall calorimeter was used as the experimental apparatus.
The conventional cooling process method with a water calorimeter was discussed critically, and it was clarified that the cooling process method could not be employed anymore for nonmetallic materials, owing to the pronounced lack of the temperature uniformity within the specimens. It has been considered that the heating process using an adiabatic calorimeter is of great advantage for attaining the thermal equilibrium in the specimens, and a proper experimental condition was established in the present study.
The obtained results for the thermodynamic quantities agree well with the reliable published data. The free energies of mixing of the lead chloride-zinc chloride binary melts present an anomalous behavior corresponding to the observed anomalies in the other physical Droperties of the melts.

View full abstract

Interdiffusion coefficient, \ ildeD, in Cu–Mn alloys has been determined by Matano’s method in the temperature range between 1021 and 1203 K with the various couples consisting of pure copper and Cu–Mn alloys. It has been found that \ ildeD increases with manganese content up to 30 at%Mn and decreases remarkably with a further increase of manganese. The concentration dependence of both the activation energy and the frequency factor for interdiffusion shows a small peak at 20 at%Mn and a very large peak at 80 at%Mn; the former is attributed to the increase in rigidity of the alloy and the latter to the deviation of the alloy from the ideal solid solution. The Kirkendall marker has been found to move toward the manganese-rich side where the Kirkendall void has been observed, indicating that the manganese atom diffuses faster than the copper atom. From the interdiffusion coefficient and velocity of the marker, the intrinsic diffusion coefficients, D_Mn and D_Cu, in 29 and 77 at%Mn alloys have been determined, and it has been shown that the ratio of D_Mn⁄D_Cu takes the value between 1.5 and 2.9.

View full abstract

It is well known that an aluminum single crystal having a ⟨100⟩ tensile orientation shows initially rapid hardening and subsequently, after about several per cent elongation, the tensile stress-strain curve becomes very flat until failure. It has been reported that the prominent cross slip which does not usually occur in aluminum but does, for example, in α-brass, was observed in this flat region of the curve. However, many problems of the relation between the deformation mode and the stress-strain curve of the ⟨100⟩ oriented single crystal remain unsolved as yet.
In the present paper, the ⟨100⟩ oriented aluminum single crystals were tested in tension at room temperature and the deformation mode was examined by observations of the slip lines and the changes in orientation of the tensile axis.
Initially, the flow stress of the ⟨100⟩ oriented single crystals increased rapidly due to multiple slip. After about 2% elongation, clustered slip accompanied by prominent cross slip was formed and the deformation proceeded by the propagation of this clustered slip, just like the Lüders band deformation. Therefore, the flow stress of the single crystals became constant. After about 20% elongation, the tensile orientation of the single crystals deviated from the ⟨100⟩ axis as a result of the deformation by clustered slip, and slip systems suitable for the deviated tensile orientation which were not accompanied by prominent cross slip were activated.
The occurrence of prominent cross slip in aluminum crystals primarily depends on the ratio of shear stress on the cross slip system to that of the primary slip system, and in a crystal having a large value of this ratio, i.e., the tensile orientation near the ⟨100⟩ axis, prominent cross slip occurs.

View full abstract

It is well known that an aluminum single crystal having a ⟨100⟩ tensile orientation shows initially rapid hardening and subsequently, after about several per cent elongation, the tensile stress-strain curve becomes very flat until failure. It was reported by the present authors that propagation of clustered slip accompanied by prominent cross slip was observed in this flat region of the curve. Similar stress-strain curves were reported in the ⟨100⟩ oriented gold and silver single crystals deformed at room and high temperatures, respectively. However, the details of deformation behavior of copper single crystals having a ⟨100⟩ tensile orientation still remain unclear.
In the present study, the ⟨100⟩ oriented copper single crystals were tested in tension at 473, 293 and 77 K in order to clarify the mechanisms of deformation. The effects of tensile orientation and deformation temperature on the occurrence of prominent cross slip were studied.
Prominent cross slip occurred in the ⟨100⟩ oriented copper single crystals and was observed more frequently with increasing deformation temperature. However, it was found that the frequency of prominent cross slipping in the copper crystal was much fewer than that in aluminum crystal, and the flat region of the stress-strain curve was not observed. The difference in deformation behavior between copper and aluminum crystals is considered to be due to the difference in stacking fault energy between these two metals.

View full abstract

The present study was made in the hope of preparing a large synthetic single crystal of cryolite. As a result of many attempts, the hydrothermal synthesis is proved to be most satisfactory. The cryolite crystal grown is as large as 2.0×1.5×0.8 mm and free from the OH radical.
The characterization of the synthetic cryolite is investigated by the differential scanning calorimeter and the Raman spectrometer.
The specific heat for the synthetic cryolite is expressed as a function of temperature:
C_p=183.9+141.9×10⁻³T.
The force constants of stretching, deformation and non-bonding for the synthetic single crystal of cryolite are (3.63±0.025)×10², (0.41±0.013)×10² and (0.30±0.00)×10² Nm⁻¹, respectively.

View full abstract

Phenomenological calculations have been carried out on the crystallographies of non-thermoelastic and thermoelastic martensitic transformations in Fe–Pt alloys near the composition Fe₃Pt, using the theory developed by Wechsler, Lieberman and Read and the crystallographic data recently accumulated. The calculated habit plane normals, directions of the shape strain, and relative twin widths of (112) transformation twins are not greatly different by the type of martensitic transformations. The magnitudes of total shape strain and lattice invariant shear are smaller for the thermoelastic type transformation. Particularly, the normal component of the total shape strain to the habit plane is much smaller for the thermoelastic type transformation roughly by one order of magnitude. The orientation relationship between the austenite and martensite lattices approaches the Nishiyama’s as the transformation becomes thermoelastic. It is thus concluded that the distinct difference between the two types of martensitic transformations exists in the magnitude of the normal component of the total shape strain. This conclusion is also rationalized by a comparison of the thermoelastic Fe-Pt martensite with a non-thermoelastic Fe–Al–C martensite whose crystallographies are very similar to those of the former martensite.

View full abstract

The eutectic solidification of Fe–Ni–C, Fe–C and Fe–Si–C spheroidal graphite cast irons were investigated quantitatively. Small specimens of the irons were quenched at various stages of solidification under controlled cooling, and their microstructures in vertical sections were examined.
The number of the growing graphite nodules or eutectic spheres in unit volume of the iron was found unchanged from the beginning of normal solidification. The growth rate constants of eutectic spheres obtained in a varied condition of undercooling were consistent with those calculated on the assumption that the growth was controlled by the carbon diffusion inward through the austenite envelope.
An approximate interrelation between the fraction and number of graphite nodules, the growth rate constant of eutectic spheres and the solidification time was obtained. From the equation and the saturated value of the growth rate constant, the critical conditions for the abnormal solidification to occur in the later stage were considered and verified experimentally. The relationship between undercooling and the number of graphite nodules in castings of the same solidification period was also successfully explained.

View full abstract