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Mn, Al, and C powder mixtures were mechanically alloyed using a conventional ball mill and a high-energy ball mill in an argon atmosphere. Although the mechanically alloyed powders prepared by the conventional ball mill retained the original powders, the powders prepared by the high-energy ball mill did not retain the original powders and consisted of α-Mn solid solution. However, no intermetallic compounds such as the magnetic τ phase and high temperatures e phase were formed during the mechanical alloying. The magnetic τ phase was obtained by subsequent annealing of the mechanical alloyed powders as was the case for the gas atomized powders. It was found that annealing of the powder mixture, without mechanical alloying, resulted in the formation of the small amount of the magnetic τ phase. However, the mechanical alloying significantly increased the amount of the magnetic τ phase in the annealed powders. This was due to the thorough mixing of Mn, Al, and C powders by the mechanical alloying. The magnetic properties of the annealed powders were deeply dependant on the annealing temperature. The optimally annealed mechanical alloyed powders showed a large saturation magnetization with a high coercivity comparable to those gas atomized counterparts.

The synthesis of single-phase CrB was succeeded by self-propagating high-temperature synthesis (SHS) in an argon atmosphere from an elemental mixed powders (Cr: ≤ 2μm and B:0.2μm) preheated at 300° to 600°C in a reduced pressure. The dense monolithic CrB ceramics ( ≥ 98% of theoretical) were obtained by hot-isostatically pressing CrB powder for 2h under 196 MPa at 1200°to 1500°C. They revealed excellent mechanical properties: Vicker's hardness Hv-23.3 GPa, bending strength σb-690 MPa and fracture toughness KIC- 6.6MPa⋅m1/2.

Elemental powders of chromium and silicon have been mixed to give the desired composition of Cr-66.66 at%Si and milled in a planetary ball mill under an argon atmosphere. CrSi2 has been synthesized in situ during ball milling. The obtained powder milled for 360ks consisting nano-sized Cr, Si and CrSi2 enables us to prepare dense compacts at the consolidating temperature 1290K which is about 170K lower than that of the other milled powders for various times. This is due to a decrease of powder particles and grains. Power factor of Cr-66.66 at%Si compact prepared by mechanical alloying and pulse current sintering is higher than that of other silicides below 650K, and shows the maximum value of 1.4×10-3 (W⋅K-2⋅m-1) at 550K.

Elemental Ti and Fe powders were mechanically alloyed using a high-energy ball mill and a conventional ball mill in an argon atmosphere. The morphology, structure, and hydriding behavior of the resultant powders were compared. The powders milled for 100h using a conventional ball mill consisted of Ti and Fe phases together with TiFe phase. On the other hand, those milled for 100 h using a high-energy ball mill consisted mostly of the TiFe phase together with a small amount of Ti and amorphous phases. The mechanically alloyed powders were easily absorbed hydrogen after one step activation with heating at 723 K in vacuum and subsequent hydrogenation at room temperature. The characteristics of the pressure-composition-temperature (PCT) curve were deeply dependent on the amounts of Ti and TiFe phases in the mechanically alloyed powders. The powders milled for 100 h using a high-energy ball mill had a lower plateau pressure than those milled for 100 h using a conventional ball mill. These mechanically alloyed Ti-Fe powders had a lower plateau pressure than the fully activated Ti-Fe alloy counterparts.

Fe-48at%Cr alloy powder was synthesized by mechanical alloying (MA) of a powder mix of Fe and Cr using a planetary ball mill for 324 ks under 1.33-kPa argon atmosphere. The MA powder was mixed with 50, 60, 70, 80 and 90 mass% MJSi2 by the same planetary ball for 36 ks. The obtained mixtures were sintered at 1273K for 0.3 ks through pulsed current sintering (PCS) process.Temperature of the start of shrinkage decreased with increasing amount of MA powder in the mixture. The shrinkage of MoSi2-50mass% (Fe-48at%Cr) powder started at a temperature about 200 K lower than that of MoSi2 powder. But, We found that reacted layer was formed at the interface between MoSi2 and Fe-48at%Cr, for the compositions of rich Fe-48at%Cr.MoSi2-30mass%(Fe-48at%Cr) composite showed higher oxidation resistance than MoSi2 in the air at 1273 K. X-ray diffraction analysis showed Cr3O2 coat was formed on the surface of MoSi2-30mass%(Fe-48at%Cr) composite.

Si and Cu powders are added to Al powder and the mixtures compacted are heated at 620 or 600°C for 1 hr. in an argon atmosphere. Based on isothermal phase diagrams of Al-Si-Cu system(Al corner)at 620 and 600°C, the amounts of liquid phase are varied from10to60mass%. The relative densities of the sintered compacts are analyzed by using a regression analysis program; the relative densities are expressed as functions of sintering temperature, amount of liquid phase, ratio of Cu/(Cu+Si), and the others. Uniformity of shrinkage after liquid phase sintering is also analyzed.

In order to obtain aluminum alloy powder which composes of α-Al phase super-saturated with titanium and boron, the titanium and boron powders were mixed with various amounts of molar ratio Ti/B=1/2, to aluminum powder and then the mixture was mechanically alloyed for 108ks. The alloy powder was heat-treated for various times at 723-873K in argon atmosphere. It was observed that the structural change of the alloy powder with the heat-treatment by XRD, SEM and EPMA. When the Al-10-20mass%(TiB) powder heat-treated at 700-800K for treating time up to 3.6ks, Al3Ti, Al5Ti2 phases and diborid particles as TiB2 and AlB2 precipitate from the super-saturated α-Al phase, and these precipitates become to Al3Ti and TiB2 by the treating for long time. In the heat treatment at 873K for 3.6ks more than, Al3Ti phase ceased to exist, and only TiB2 existed in α-Al phase. The powder was consolidated at 873K for 5.4ks under various pressures. The Al-15-20mass%(Ti/B) alloys produced by the hot-pressing of about 300MPa become higher strength due to the precipitation-hardening and the dispersion of fine TiB2 particles.

Mo-Si-Al alloy and Mo-Si-Al/SiC composite were fabricated by the powder metallurgical process from a novel Mo-Si-Al prealloyed powder, and their microstructure and mechanical properties were evaluated. The Mo-Si-Al and Mo-Si-Al/15 vol%SiC mixed powders were hot-pressed in an argon atmosphere. XRD analyses revealed that Mo-Si-Al/SiC composites were composed of MoSi2 (tetragonal, Cllσ structure), Mo(Si, Al)2 (hexagonal, C40 structure), a-Al2O3, Mo ?? 5Si3C ?? 1 and β-SiC. Almost no glassy SiO2 phase was found in Mo-Si-Al and Mo-Si-Al/SiC systems contrary to MoSi2 and MoSi2/SiC. The formation of α-Al2O3 was attributed to the predominant oxidation of aluminum at the surface of the Mo-Si-Al prealloyed powder. Mo-Si-Al based systems showed the better high-temperature strength mainly due to the elimination of glassy SiO2 and the crystallographical change from t-MoSi2 to h-Mo(Si, Al)2. Incorporation of fine SiC particles enabled to control microstructure and then to enhance mechanical properties.

Quasi binary SiC-B4C and ternary Si-B-C system composites were prepared by arc melting in argon atmosphere. The Vickers microhardness (100g load) of the quasi binary SiC-B4C composites decreased from 39 to 34 GPa with increasing SiC molar content (mSiC) from 25 to 65 mol%. The hardness values at mSiC=45 to 55 mol%, which is nearly the eutectic composition, was higher than those calculated from a linear law. This could be caused by fine lamella microstructures. Free C and free Si co-precipitated at the C-rich and Si-rich side of the quasi binary composition, respectively. The hardness values at the quasi binary compositions were greater than those of the C-rich and Si-rich compositions.

Effect of mechanical grinding (M.G.) process on preparing β-FeSi2 for thermoelectric generator by useing hot presssing (H.P.) was investigated by X-ray diffraction, EPMA and SEM.Mixture of Fe and SI powders was arc-melted in an argon atmosphere to form a button composed of α-Fe2Si5, and e-FeSi phases. The button was grinded in a conventional ball-mill for 20-650hr. X-ray diffraction analysis showed that the peaks of e and α-phases disappeared after 250 and 650hr, respectively. The ball-milled powders were hot pressed at 1110°C for 30min under 25MPa and heat treated at 840°C for 10hr and 20hr. The heat treated samples were composed of mostly β-phase with small amount of e-phase and their relative densities were more than 99%. The amount and size of the e-phase decreased with increasing ball milling time. The result showed that mechanical grinding strongly accelerated the formation of β-phase. Almost the same results were obtained oil hot pressing at 900°C for 30min without heat treatment.

Mechanical alloyed mixtures of elemental Fe and Si powders with compositions FexSi100-x (10≤X≤50) have been characterized in the as-milled condition, as well as after heat treatments. Ball-milling in an argon atmosphere first induces alloying of the elements, followed by the formation of FeSi(e) compound in the mixture of Fe50Si50, and FeSi2(β) compound in the mixture of Fe30Si70. Upon heating a Fe30Si70 mixture previously milled for 720ks, transformation to an almost single phase FeSi2 occurs, with the exothermic reaction at around 723K. The MA powders milled for 720ks, heated to temperatures between 1173K and 1273K and air cooled, exhibited the phases. expected from the Fe-Si phase diagram. A substantial enhancement of the (Fe2Si5(α) + e) to β transition was observed in the MA powders of Fe30S70 composition in which the β phase formed from (α+e) during furnace cooling from 1273K. This enhancement of the (α+e) to β transition is considered to be due to the enhanced diffusion resulting from the refinement of grain sizes of the α and e phases after MA.

Mixtures of Si3N4, and Ti were milled with a high energy ball mill under argon atmosphere and successively sintered with a hot press. The resulted reaction products were fine mixtures of Ii5 Si3, TiSi2, IN and Si, their fractions varying according to initial compositions, milling time and sintering temperatures. The temperatures at which sintering proceeded was much lower than that for sintering of Si3N4, again depending upon compositions and milling time. The density of sintered products was high enough with hardness comparable to that of TiN. Sound indentations without cracking were noted.A model based on kinematical rather than thermodynamical equilibrium aspect was presented to explain the dependence of reaction products on process parameters.

Ag30Dy70 alloy was mechanically alloyed from pure crystalline Ag and Dy powders by high energy ball milling (Fritsch "Pulverisette 7") with the speed settings 7 or 3 in an argon atmosphere. The alloying process was investigated by X-ray diffraction, optical microscopy and differential scanning calorimetry.In the first milling stages, the Ag and Dy powders have a well-aligned layered microstructure. This microstructure is typical for mechanical alloyed specimens during the early stages of milling and gets finer with increasing milling time. At this stage intermetallic compound AgDy has obtained. After 200 h of milling, the X-ray diffraction peaks of AgDy and Dy powders have hardly changed in intensity and the broad peak characteristic of an amorphous Ag30Dy70 powder was not produced by mechanical alloying from crystalline elemental powders.

The mechanism of the synthesis of SiC powder by carbothermic reduction of silica has been studied. The rate of reduction of SiO2 powder with coarse graphite particle was measured by means of thermogravimetry at temperatures from 1923 K to 2073 K under an argon atmosphere. Reduction products were investigated by chemical analysis and microscopic observation.Reduction products are both SiC and SiO. The growth of SiC layer is observed at the surface of the graphite particle.At the early stage of the reaction, the synthesis of SiC is controlled by the reaction of the gaseous compomnent, SiO with the graphite surface. The formation of the continuous layer of SiC around the graphite particles shifts the rate-determining step to the diffusion process of carbon through the SiC layer.

Amorphous NixZr100-x alloy powders (x=28, 33, 40, 45, 50, 65, 70) were synthesized by MA from crystalline powders of the elements using high-energy ball milling in an argon atmosphere. The alloying and amorphization process was investigated by X-ray diffractometry and differential scanning calorimetry.X-ray diffraction profiles taken as a function of milling time showed that, at the initial stage of MA, amorphization proceeded rapidly, that is, the preferential diffusion of Ni through Zr occurred rapidly and then proceeded slowly with increas-ing milling time. The amorphization by MA is found to depend on a large negative heat of mixing as the driving force of the diffusion. The radial-distribution functions, determined by X-ray diffractometry, are comparable to those measured for mechanical alloyed and liquid quenched amorphous Ni-Zr alloys of the same composition.