The optical basicity (Λ; Pb²⁺ as probe ion) of various oxide glass systems has been measured to establish the new basicity scale of oxyacid salt melts. Best conditions of glassy fragments to measure Λ were determined. Problems in establishing the new basicity scale using Λ-values are discussed, and also relation between Λ and Fe²⁺–Fe³⁺ redox equation is discussed in terms of Fe³⁺-constitution. Λ has the posibility of showing the Lewis and new scale of basicity in these melts.

View full abstract

The oxygen solubility curves for Fe–Ti–O, Co–Ti–O, Ni–Ti–O, Fe–Zr–O . Co–Zr–O and Ni–Zr–O alloys saturated with oxides of titanium and zirconium were calculated. The experimental data of Fe–Ti–O and Fe–Zr–O systems from the literature correlate reasonably well with the calculated curves from the model by Wagner and the empirical correlation of Chiang and Chang over the temperature range of 1823 K to 2073 K . The Gibbs energies of oxygen in liquid titanium, ΔG_O(Ti)^° and zirconium, ΔG_O(Zr)^° were also estimated.

View full abstract

Effects of minor addition of niobium (0.039 mass%) on the tempering process of 0.15 mass% carbon steel were examined by a hardness test and optical- and electron-microscopy. All the specimens were solution-treated at 1523 K and then quenched to form martensite. Some of them were deformed 50% by cold rolling prior to the tempering at 923 K.
Experimental results obtained are summarized as follows: The recovery process of the lath martensite was markedly suppressed by the presence of niobium. In the case of the as-quenched lath martensite recrystallization was not observed, while in the case of the deformed lath martensite recrystallization occurred rapidly during the tempering. The recrystallization, however, was considerably retarded by niobium addition. Such effects of niobium on the recovery and the recrystallization behavior may be related to the precipitation of niobium carbide during the tempering.

View full abstract

Aluminum and Al–Cu alloy ingots which were made from pure or commercial pure aluminum (99.99 mass%Al and 99.8 mass%Al) and electrolytic copper, were solidified unidirectionally with cooling only from the bottom. From the observation of the ingot structures and the analysis of the crystallographic orientations of the crystals in the ingots, it was proved that solidification of the ingots proceeded not only with growth of columnar crystals but also with production of free crystals, which became columnar free crystals or enclosed free crystals, and the columnar to equiaxed transition in the ingots had a transitional zone which began with the production of these free crystals and finished with the sufIicient supply of such free crystals on the freezing front to stop the competitive growth between such free crystals and the columnar crystals from the below.
It was also estimated that the most probable mechanism of the free crystals production in this kind of ingots is the “heterogeneous nucleation in the constitutionally supercooled liquid”.

View full abstract

Aluminum, Al–Cu alloy and Al–Zn alloy ingots, which were made from pure or commercial pure aluminum (99.99 mass%Al and 99.8 mass%Al respectively) and electrolytic copper or electrolytic zinc were seeded by single crystals or bundles of columnar crystals of ⟨100⟩ growth direction and solidified unidirectionally with the cooling only from the bottom. The increase of the number and the size of the free crystals during the solidification and the stopping process of the columnar crystals by these free crystals were clearly observed in the structures of the single seed crystals of the ingots. The maximum height of the columnar crystals varied with the constitutional supercooling parameter, −mC₀(1−k). The analysis concerning the signal showing the passage of the columnar crystals’ tip was described in the appendix.

View full abstract

Supercooling for nucleation of solid in solidification of small specimens of pure aluminum (99.99 mass%Al) and commercial pure aluminum (99.8 mass%Al) cooled in a furnace was measured. As a result it was found that the commercial pure aluminum contained an active catalyst for nucleation of solid when it was melted below about 1040 K (about 760°C), but the commercial pure aluminum melted above 1040 K and pure aluminum melted at any temperature did not contain such an active catalyst. The efficiency of this catalyst was so strong that it was estimated to be able to nucleate solid in the constitutionally supercooled liquid of ordinary alloy ingots.

View full abstract

The deformation structure of (211)[\bar111] copper single crystals rolled at room and liquid nitrogen temperatures (RT and LNT) was observed by transmission electron microscopy, and the microstructural process of shear band nucleation was examined. The microstructure prior to the shear band nucleation was composed of the laminated structures of twin/matrix layers at the LNT rolling and of the thin layer-like cells at the RT rolling, both of which seemed to be nearly parallel to one of active slip planes. Regions with relatively large lattice rotation (0.2–0.35 rad) were found within these laminated structures. Localized deformation at these regions appeared to contribute to the nucleation of the shear bands. It will be concluded that the nucleation process of the shear bands is closely correlated with the deformation behavior of the laminated structure developed along one of active slip planes.

View full abstract