An amorphous phase in Nd–Fe–Al system was formed in an extremely wide composition range of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Based on the information on the amorphous formation, ferromagnetic Nd_90−xFe_xAl₁₀ bulk amorphous alloys with high coercive force at room temperature were obtained by a copper mold casting method. The maximum diameter of the cylindrical amorphous samples with a length of 50 mm is about 7 mm for the 20%Fe alloy and about 4 mm for the 30%Fe alloy. Neither glass transition nor supercooled liquid region is observed in the temperature range before crystallization, being different from previous bulk glassy alloys exhibiting a wide supercooled liquid region before crystallization. The onset temperature of crystallization (T_x) and melting temperature (T_m) are measured to be 778 and 863 K, respectively, for the Nd₇₀Fe₂₀Al₁₀ alloy. The resulting reduced ratio of T_x⁄T_m is as high as 0.90 and the temperature interval between T_x and T_m is as small as 85 K. The extremely high T_x⁄T_m and small ΔT_m(=T_m−T_x) values are the reason for the achievement of the large glass-forming ability. The bulk amorphous Nd₇₀Fe₂₀Al₁₀ alloy has a ferromagnetism with the Curie temperature (T_c) of about 600 K which is much higher than the highest T_c (about 480 K) for the Nd–Fe binary amorphous alloy ribbons. The remanence (B_r) and intrinsic coercive force (_iH_c) for the bulk Nd₆₀Fe₃₀Al₁₀ alloy are 0.122 T and 277 kA/m, respectively, in the as-cast state and 0.128 T and 277 kA/m, respectively, in the annealed state for 600 s at 600 K. The B_r and _iH_c decrease to 0.045 T and 265 kA/m, respectively, for the crystallized Nd₆₀Fe₃₀Al₁₀ sample consisting of Nd+Al₂Nd+δ phases and the maximum hard magnetic properties are achieved in the amorphous state. The hard magnetic properties for the bulk amorphous alloys are presumably due to the homogeneous development of ferromagnetic clusters with large random magnetic anisotropy. The finding of the bulk amorphous alloys exhibiting hard magnetic properties at room temperature is promising for the future development as a new type of metallic amorphous permanent magnet.

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Stacking faults in an Fe-35 mol%Al alloy with the B2 ordered superlattice structure have been investigated by a diffraction contrast method of transmission electron microscopy (TEM). The detailed observation by a phase contrast method of high-resolution transmission electron microscopy (HRTEM) has also been performed on the alloy. Two types of stacking faults were observed by HRTEM. In order to interpret the experimental images, computer simulations of HRTEM images based on different fault models have been carried out. The image simulations reveal that the model of the stacking faults deduced from the diffraction contrast method of TEM (i.e. the displacement vector R=a⟨100⟩⁄2) cannot fit one type of the HRTEM images. In the present study, a possible model of the faults (R=(1−\sqrt3)a⟨100⟩⁄2) and a mechanism for their production are proposed.

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An icosahedral Al₇₀Pd₂₀Mn₁₀ quasicrystal was etched under several etching conditions with solutions composed of HF and H₂O plus HCl and/ or HNO₃. The formation of etch pits was examined closely by scanning electron microscopy and replica electron microscopy. When etched for 5 s at 293 K with the etchants of different compositions, the faceted pits were often observed except for a few exceptions. All those pits revealed the similar shape of pentagonal dodecahedron where the pentagonal faces were curved slightly near their corners and edges. By etching for 5 s with a solution of HF+HCl+H₂O (1:3:5 in volume ratio), the average size of the pits decreased from 4.5 to 2.5 μm with an increase of etching temperature from 273 to 333 K, and the pentagonal faces tended to be flattened above 313 K. The pentagonal faces near the corners and edges of the pits became more curved and the average size remained unchanged (∼4.5 μm) with increasing etching time in the range of 1 and 20 s at a temperature of 293 K. By comparing the surfaces before and after etching at the same areas, it was concluded that the faceted pits originated from irregular small holes which pre-existed on the polished surface.

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Non-stoichiometric CrN_1+x (0.0≤x≤0.2) thin films with a NaCl-type structure have been prepared by reactive sputtering of chromium metal target in Ar/N₂ mixed gas. Nearly stoichiometric CrN thin films are obtained at the N₂ mixing ratio of 20% and the total pressure of 0.67 Pa. Magnetic susceptibility, electrical resistivity and X-ray diffraction measurements indicate that these films show an antiferromagnetic first order phase transition at around 260 K. With the increase in N₂ partial pressure, metastable over-stoichiometric CrN_1+x thin films are obtained. The compositions of samples prepared in pure N₂ gas are almost CrN_1.2 and the lattice constant is 2% greater than that of the nearly-stoichiometric bulk CrN. Over-stoichiometric CrN_1+x thin films do not show the first order antiferromagnetic phase transition. Their χ-T curves show a broad maximum at around 90 K. The electrical resistivity at room temperature decreases with increasing the nitrogen composition and the temperature coefficient of resistivity is always negative. The composition dependence of magnetic and electrical properties correlates to the variation in the density of state near the Fermi level detected by XPS.

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The powder of supersaturated solid solution of Al-7.8 at%Ti-0.3 at%Fe with a nanocrystalline structure was prepared by mechanical alloying, and it was compacted to columnar shape material at low temperature by application of high pressure of 3 GPa. Diffusion of copper was studied in this compacted nanocrystalline material using an ion mass microanalyzer. The interfacial diffusion coefficient of copper in the nanocrystalline materials is fairly higher than the volume diffusion coefficient of copper in aluminum, and the activation energy of the interfacial diffusion is quite small when compared with that of volume diffusion of copper in aluminum. The characteristic of the interfacial diffusion implies that the interface in the nanocrystalline materials of this research should have a very loose structure.

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In order to design a new kind of high-temperature Fe–Cr–Ni alloy with good weldability which could be used as structural material of Iron-ore sintering furnaces and Magnesium-smelting tanks, effects of additions of carbon, nickel, and molybdenum to Fe–Cr–Ni alloy on strength at 1250°C have been studied. The rupture strength at high-temperature of the alloy is mainly determined by grain-boundaries. Addition of carbon to the alloy can affect the morphology of the precipitates at grain-boundaries apparently. With increasing carbon content, the rupture strength increases significantly at first, and then begins to decrease acutely when carbon content exceeds about 0.43%. The addition of nickel increases the alloy strength until its content reach about 10%, further addition of nickel will slightly decrease the alloy strength. The effect of molybdenum on the strength is similar to that of nickel, the maximum value of the strength is obtained by the addition of 0.30% molybdenum. However, neither nickel nor molybdenum could obviously affect the microstructure of the alloy.

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The water-soluble titanyl acylate precursor, prepared by titanium (IV) isopropoxide with glacial acetic acid, was used in alkaline solution (pH>13) to precipitate ultrafine La₂O₃-doped SrTiO₃ powder with various Sr/Ti ratios. The Magneli phase (Ti_nO_2n−1) was found in the grain boundary of the SrTiO₃ sintering body with titanium in excess, easier to be sintered, and having a liquid phase existed in the grain boundary, resulted in an anomalous increase in the dielectric constant (at 1 kHz) up to 87000 at 1623 K. On the contrary, the phase of Sr_n+1Ti_nO_3n+1 (n=1, 2 or 3) were found in the Sr-excess SrTiO₃, and had 97% relatively density with better dielectric properties were obtained.

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In order to develop a method of gas nitriding of austenitic stainless steels without chemical treatment such as pickling, three types of steels, SUS304, SUS316 and SUS310, were pretreated under various mechanical processes (as-cut with resinoid blade, polishing with emery papers, grinding with CBN wheel, and shot peening), followed by nitriding in NH₃ gas with a flow rate of 2.8 m³/h at 843 K for 20 h. The influence of the mechanical pretreatment on nitriding behavior was examined in connection with two factors of surface roughness and strain-induced martensite.
Nitriding reaction depends primarily on surface roughness in SUS310 and SUS316. This nitriding reaction is markedly enhanced with increasing surface roughness when its value exceeds 6 and 1 μm for SUS310 and SUS316, respectively, while no reaction is recognized for the surface roughness less than these values. In SUS304, martensitic transformation is readily induced by the mechanical pretreatment, and not only the surface roughness but also the strain-induced martensite contribute to nitriding behavior.
It is confirmed from the present results that mechanical pretreatment enables the gas nitriding of austenitic stainless steels without pickling, when the surface roughness and the amount of strain-induced martensite are controlled properly.

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In the metal injection molding process, it is very important to sinter the debound compact of very low density to a high dense compact while keeping its initial shape.
The effects of silane treatment on the sinterability of injection molded Fe, Fe–Si and Fe–Co powder compacts were investigated. The treatment was done in such methods as to coat the powder particles with a silane coupling agent, or to add it directly to the organic binder in hot mixing.
The results obtained were as follows:
It was shown that the densification of the injection molded Fe and Fe–Si compacts during sintering was markedly accelerated by the silane treatment. The sintering enhancement was pronounced especially at relatively low temperatures of 1373 to 1453 K, and the effect of silane was only realized in the case of the injection molded compacts. The optimum quantity of the silane as an enhacer for the injection molded compacts was estimated to be about 0.2 mass%. It was also shown that the linear shrinkage of the silane coated powder compacts during sintering occurred more isotropically than that of the compacts with silane directly mixed or without silane.

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Using Sm_2.5Fe₁₇ alloy powder of −100 mesh, the preparation of Sm₂Fe₁₇N_x magnetic powder whose grain size is finer than the single magnetic domain size was carried out by mechanical grinding (MG) and subsequent heat treatments for crystallization, nitriding and annealing. The effects of MG time and heat treatment on the factors such as the grain size, nitrogen and oxygen content, the precipitation of α-Fe and magnetic properties have been investigated. The results obtained are summarized as follows:
(1) The grain size of powders after MG was about 10–30 nm and it was extremely finer in comparison with the single magnetic domain size of about 300 nm. Although the grain size was coarsened by the subsequent heat treatments, it was about 50 nm even after annealing.
(2) The precipitation of α-Fe was caused by the oxidation of powder, and it was confirmed that the oxygen content of the powder should be lower than 9000 ppm in order to prevent the α-Fe precipitation.
(3) The maximum coercivity of 2.24 MA·m⁻¹ was obtained under the following condition; i.e., MG time: 108 ks, crystallization: at 1023 K for 1.8 ks, nitriding: at 723 K for 129.6 ks and annealing: at 623 K for 7.2 ks in N₂.

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Molten salts based on equimolar (NaCl–KCl) with small addition of fluorides are usually used in remelting secondary aluminum alloy scrap such as Used Beverage Cans. In this work, the surface tension of equimolar NaCl–KCl with addition of NaF, LiF, KF, and Na₃AlF₆ have been measured by the pin detachment method. Addition of fluorides into NaCl–KCl increases the surface tensions of molten salts. The experimental results are compared to the Guggenheim model as well as the modified Guggenheim model. The binary modified Guggenheim model can give reasonable estimates for ternary salt systems. The density of these molten salts is also found to increase by the addition of fluorides. The implication of the surface tension and density data on ternary salt systems in remelting process is discussed.

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The recycling/remelting of thin aluminum scrap generally involves melting of these pieces submerged in molten salt. These pieces are originally covered with a thin oxide film. The oxide film must be first removed by molten salts before coalescence between the drops can occur. In this study, two new experimental techniques were designed to study the oxide film removal and the droplet coalescence in the molten salt. The effects of alloy and salt compositions on the oxide film removal and the drop coalescence were studied. Mg content in Al alloy results in a thicker oxide film on the metal piece and its removal was found more difficult. However, the fluoride addition facilitated the oxide film removal. The paper discusses various oxide film removal mechaisms. The second of the two experimental techniques included bringing two molten metal drops together and noting the time required for the drops to coalesce. These experiments provided a quantitative measure of the coalescence ability of various salts. Metal drops could not coalesce in the pure chloride (NaCl–KCl) molten salt. Alloys containing Mg reacted with salt to produce Na or K which makes the surrounding salt as purple bluish in color which is termed as “fog”. Mg containing alloys produced dense “fog” and retarded the coalescence of the metal drops, while Mn, Si, and Fe had little effect on “fog” formation and coalescence.

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Cylindrical glassy alloys with diameters up to 40 mm were prepared for a Pd₄₀Ni₁₀Cu₃₀P₂₀ alloy with a high reduced glass transition temperature (T_g⁄T_m) of 0.71 by water quenching the molten alloy in the quartz tube. The bulk glassy alloy with a diameter of 40 mm exhibits good metallic luster on the outer surface. Neither cavities nor voids are seen over the whole inner region and no contrast revealing a crystalline phase is seen over the transverse cross section. The glass transition temperature (T_g), crystallization temperature (T_x), the temperature interval of the supercooled liquid region (ΔT_x=T_x−T_g) and the melting temperature (T_m) are measured to be 575, 95 and 804 K, respectively, for the Pd₄₀Ni₁₀Cu₃₀P₂₀ alloy with a diameter of 40 mm. The deviation of Cu content from 30 at%Cu in the Pd₄₀Ni_40−xCu_xP₂₀ system causes a steep increase in T_m and a decrease in T_g⁄T_m, leading to the decrease in the glass-forming ability. The successes of finding the new Pd–Cu base alloy composition with the large ΔT_x and T_g⁄T_m values and preparing the bulk glassy alloy with a diameter of 40 mm are encouraging for the future development of glassy alloys.

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A bulk glassy Zr₅₅Al₁₀Ni₅Cu₃₀ alloy in a cylindrical form with a diameter of 30 mm and a length of 50 mm was produced by sucking the molten alloy into a copper mold. The sucking force was generated from the rapid movement (5.0 m/s) of piston with a diameter of 30 mm which was set at the center of the copper hearth. The sucking velocity is evaluated to be as high as 22.1 kg/s. Neither cavity nor hole is seen in the transverse cross section of the bulk glassy alloy. The glass transition temperature (T_g), crystallization temperature (T_x) and supercooled liquid region defined by ΔT_x(=T_x−T_g) are nearly the same as those for the melt-spun glassy ribbon with a thickness of 30 μm, in spite of the significant difference in sample thickness by three orders. Furthermore, there is no appreciable difference in T_g, T_x and ΔT_x over the whole cast sample. The Vickers hardness number is 523, in agreement with that (\fallingdotseq 510) for the corresponding melt-spun glassy ribbon and cast bulk glassy cylinders with diameters below 15 nm. Thus, the direct production of the bulk glassy alloy with a diameter of 30 mm by the suction casting method is important for the future development of bulk glassy alloys.

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