The Cu–Sn binary diffusion couples were annealed in the temperature range of 190 to 220°C. Diffusion coefficients in the η and ε phases as well as the Kirkendall effect were measured. Kirkendall markers moved toward the Sn side and consequently the movement suggests the preferential diffusion of Sn atoms by a vacancy mechanism.
The Cu–η, α–η and δ–η couples were annealed in the temperature range of 357 to 404°C. There was only one ε phase layer in each diffusion zone of the three types of couples. The ε phase in the δ–η couple grew at the highest rate in spite of the fact that it had the smallest diffusion coefficient. It may be concluded that the concentration gaps between the ε and its neighboring phases are most effective on the growth of the ε. From this point of view, it was possible to predict what phase layer should preferentially grow in the reaction diffusion of five binary systems.

View full abstract

Fan-type microcrystals of Zn and Cd that are new in form are found. They were grown under the condition of an Ar-gas pressure of 160 Torr and a supersaturation ratio of eight. The crystals became several hundred μm in the radial direction and several tens of μm in thickness. They were of two types, one of which was a single crystal and the other was a contact twin with a (0001) plane as a rotation boundary.
A new method was given to classify the rotation boundaries by the arrangement of atoms on a coincidence boundary. The findings about fan-type microcrystals by scanning electron microscope were also reported together with the twinning of the crystals. Finally, three new types of rotation boundaries were added to nine of those that had been classified according to the difference in Laue transmission patterns.

View full abstract

Correlations between maximum solid solubilities at two component sides in the phase diagrams were analyzed by using a linear arrangement of the elements related to their melting points. Thus discovered empirical rule can be applied for 91% of possible 369 systems and further it may be correlated with the activity curves at two component sides.
From thermodynamic analysis of liquidus lines in the phase diagrams the activity deviations from Raoult’s law over a high concentration range were estimated. The results lead to the conclusion that there are many cases where the activities do not obey Raoult’s law even at an extremely high concentration near pure components and the activities of such systems can be explained satisfactorily by the derived relation, a_i=N_i^1⁄m_i.

View full abstract

The grain size effect on the apparent yield and flow stresses up to 20% strain has been investigated in polycrystalline copper and Cu–Al alloys of various grain sizes at 77 and 293 K.
The apparent yield stress satisfies the Hall-Petch relation in all specimens. In copper, however, the flow stresses cannot be expressed by a simple linear function but they are subdivided into two groups characterized by different linear functions of the inverse square root of the grain size. These flow stresses of copper can be roughly expressed by a single linear function of the inverse of the cell size determined by the amount of deformation, as in the case of aluminum. On the other hand, the flow stresses up to 20% strain are satisfied with the Hall-Petch relation in deformation of Cu-6.11 wt%Al alloy.
The discrepancy between copper and Cu–Al alloys is discussed in terms of the effect of stacking fault energy on macroscopic and microscopic deformation modes.

View full abstract

The crystal structure and internal defects of the banded martensite in a quenched Cu-24.5 wt%Sn alloy have already been investigated by Nishiyama et al. However, since their results are rather unexpected in some respects, the crystal structure and the morphology were reexamined by means of electron microscopy and selected area electron diffraction. Consequently, the following different results were obtained. (1) The crystal structure of the banded martensites was a 18R type long period stacking order structure with a stacking sequence of AB′CB′CA′CA′BA′BC′BC′AC′AB′. (2) The internal defects of the martensites were stacking faults on the basal plane. (3) The habit plane of the martensites was close to the (\bar1\bar44)_β1 plane, consistent with the result of Greninger and Mooradian, which was determined by the two-surface analysis in bulk specimens. (4) The orientation relationship between matrix and martensite was consistent with the Kajiwara-Nishiyama relationship found in a thermally formed β₁′ Cu–Al martensite. (5) These results were compared with the so-called phenomenological theory, and good agreement was obtained between them.

View full abstract

Tensile creep tests of WC-10%Co and WC-10%TaC-10%Co alloys were carried out at temperatures 750–950°C and stresses 5–30 kg/mm². In the case of WC-10%Co alloys, the steady state creep rate decreases, the ruptured time increases and the fracture strain decreases with increase in carbide particle-size. The steady state creep rate is approximately proportional to inverse square of carbide particle-size. With TaC addition, the steady state creep rate remarkably decreases and the ruptured time increases. The creep deformation may be controlled by the two processes, i.e. (a) diffusional flow of vacancies in the binder phase, and (b) dislocation climb over the carbide particles.

View full abstract