A high performance hydrogen storage alloy V-16 mass%Ti-12 mass%Ni-1.4 mass%Nb-0.96 mass%Co-2.8 mass%Ta is sensitively influenced by dissolved aluminum and oxygen, both of which are reduced by unproductive refining process. Then, it was necessary to develop the process of simply removing these impurities at a reasonable cost. Then, we propose a new production technique. A V-15 mass%Ni-1.8 mass%Nb precursor with a low enough level of aluminum was produced by aluminothermic reduction of the mixture V2O5, Nb2O5 and nickel. When the V-16 mass%Ti-12 mass%Ni-1.4 mass%Nb-0.96 mass%Co-2.8 mass%Ta alloy was obtained by alloying the precursor and the other constituents of titanium, cobalt and tantalum, it was deoxidized to a low enough level by adding mischmetal as a reducing agent. By the method described here, the vanadium-based alloy can be produced at a reasonable cost.
We investigated the breakaway behavior of the surface oxide film on Al-Si-Mg alloy powder particles by X-ray photoelectron spectroscopy using synchrotron radiation (SR-XPS), which is the topmost surface analysis method with less than 1.5 nm analysis depth and has high sensitivities. During heating the powders up to 823 K, the magnesium dissolved in the powder particles was concentrated to the surface oxide below 670 K, and saturated in the composition with a Mg/Al ratio of about 0.5. Over 670 K, the metallic aluminum appeared on the topmost surface of the particles. We speculated that the surface reaction were due to the reduction of surface oxide film by the concentrated magnesium or the breakaway of the surface oxide film by the crystallization of MgAl2O4.
The microstructures and morphology of Fe-Zn alloy electrodeposited at different chloride bath compositon are studied in detail using TEM, SEM, and XRD. And comparisons are made between microstructures in Fe-Zn alloy thus deposited and those appear in a thermal equilibrium phase diagram. The results indicate that α, Γ, Γ1, and η phase appear in the Fe-Zn electrodeposit, however δ and ζ phases which appear in the thermal equilibrium phase diagram did not appear. The surface appearance and microstructures (including grain size and lattice constant) of intermediate phases in Fe-Zn alloy electrodeposites depend on the Zn content in the Fe-Zn alloy deposit. It is also found that there is an orientation relationship among the Γ, Γ1, and η phases when these three phases appear simultaneously.
It has been widely accepted that the structure of plated films differ, depending on the kind of plating solution and the plating conditions. However, the authors believe that the structure of plated films is independent of both the kind of plating solution and the plating conditions, and mainly depends on the composition of plated films. Namely, we are of the opinion that the plated film is a completely metallic material. The reason that the above theory has been believed so far can be attributed to the lack of knowledge on the structure change caused by the change of solution in the vicinity of the cathode surface during plating. In this investigation, the relationship between the conditions of the plating solution near the cathode surface and the structure of the electroplated alloy film are discussed in detail. The structure of the electrodeposited Ni-Sn alloy films was analyzed using the X-ray diffraction method and the cross sectional structure of the plated film was observed by transmission electron microscopy. It was found that the chemical reaction on the cathode surface changed due to the pH rise during plating, which caused the compositional change in the plated film resulting in the change in its structure. As a result, the plated film had a layered structure in the thickness direction. However, the addition of glycine to the bath was effective for electrodepositing a homogeneous film free from a layered structure.
Directional solidification experiments were conducted for polyvinylidene fluoride (PVDF) or copper fiber reinforced pure succinonitrile (SCN) or SCN-2.2 mass% acetone alloy composites in order to investigate the effect of fibers on dendrite growth of matrix alloys. The relative distance (ΔL) (i.e., the length between the dendrite tip in the fiber-reinforced region (composites) and that in the unreinforced region (bulk) along the heat flow direction) varies according to fiber species and growth rate. In PVDF fiber reinforced pure SCN specimens, ΔL increases as the inter-fiber spacing decreases. The difference of thermal diffusivity between matrix and fibers should change the cooling rate of the matrix among the fibers. ΔL increases more in PVDF fiber reinforced SCN-2.2 mass% acetone alloy composites than in pure SCN specimens. Furthermore, the curvature of dendrite tips and the growth rate of the secondary dendrite arm in the composites decrease because the fibers restrain the solute diffusion and enrich the solute around dendrites. ΔL decreases with increasing gap between the fiber and glass because the heat flow and solute transport may become faster through the gap and the apparent thermal and solutal diffusivity approach those in bulk material.
The distribution of hydrogen in Ni3Al intermetallic compounds doped and undoped with boron was investigated by means of tritium TEM autoradiography. The room temperature brittlement of the compound had been explained to be due to the hydrogen embrittlement, and it is well known that a small addition of boron improves the ductility drastically. In the present work, no correlation between the distribution of silver particles, which corresponds to the positions of the trapped tritium, and the grain boundaries was observed, regardless of doping boron or not. The particles were observed nearby the dislocations and grain boundary dislocations. A large amount of particles were observed for the nickel irradiated compound, which contains much voids and dislocations. These results indicate that the static hydrogen trapping sites are not effective for improving the ductility, and support the model in which the mobility of hydrogen through dislocations is retarded by doping boron.
A model for the calculation of mechanical strength based on the results that calculated from precipitation and recrystallization models proposed by authors, were uned to simulate the variation of yield strenght during annealing process. The simulated results were compared with experimental results for a Cu-Cr alloy. The calculation is based on the solid state strengthening theories. In the calculation model, four types of strengthening mechanisms; (1) precipitation hardening, (2) grain fined hardening, (3) solute solution hardening, and (4) work hardening, were considered. In the precipitation hardening model, three types of mechanisms; (1) coherent strain hardening, (2) ordering haedening and (3) bypassing hardening, were calculated. By adopting the minimum values in calculation results at various types of precipitation hardening mechanisms for the calculation of yield strenght, it was confirmed that the results based on the calculation were in good agreement with ones based on the experiments.