Amorphous Ti50-Ni50 powders prepared by MA were sintered by HIP above 700°C to obtain the compacts with non-equilibrium phases.The x-ray diffraction peaks of the specimen obtained at 700°C were relatively weak and broad.On the other hand, the specimen obtained at 900°C consisted of TiNi, Ti₂Ni and Ni₃Ti with relatively sharp peaks in the x-ray diffraction pattem.The compacts obtained may be in the non-equilibrium states leading to the equilibrium phase of TiNi.The most amorphous like compact was obtained at 700°C for lhr under 200MPa and its density was 6.2g/cm³ corresponding to 94% of the density obtained at 900°C.The grains in the compacts obtained at 700-800°C maintained the shape formed by MA, while the micro structure obtained at 900°C was largely different.The Vickers hardness of the compact obtained at 700°C was 900Hv compared with 800Hv at 900°C.The electric resistivity of the compact obtained at 700°C was 2 times higher than that of TiNi alloy.Anodic polarization curves of the compacts indicated high corrosion resistance in the compact obtained at low Hipping temperature.It was concluded that the high density compact of Ti-Ni was obtained keeping some properties of amorphous metal using low temperature HIP of amorphous Ti-Ni powders.

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The preparation of Sm₂Fe₁₇N_X permanent magnetic powder whose grain size is finer than the single magnetic domain size of about 300nm has been tried by mechanical grinding(MG) and the subsequent two-step heat treatment; namely the first one is crystallization treatment and the second one is nitriding treatment. The results obtained are summarized as follows:
1)The specimen obtained by MG(as MG'cd specimen) was composed of α-Fe and Sm-Fe amorphous phase, and this MG'cd specimen was found to turn into Sm₂Fe₁₇ phase after crystallization and Sm₂Fe₁₇N_X phase after nitriding.
2)Though the grain coarsening was observed after the two-step heat treatment, the grain size was about 50nm which is much finer than single magnetic domain size of 300nm.
3)The remarkable increment of oxygen content in the specimen was observed by the crystallization treatment. However, such an increment of oxygen content was hardly observed by the nitriding treatment.
4)The maximum cocrcivity of 28 kOc was obtained by the following condition;i.c., MG time:108ks, heat treatment:at 1023K for 1.8ks, nitriding treatment : at 723K for 129.6ks and annealing treatment : at 623K for 7.2ks in N₂.

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Combustion synthesis process has been taken an interest in synthesizing technology of intermetallic compound such as Ni₃Al. However, the synthesized compound tend to be porous, and the synthesis process has not been used practically. To realize the process, a method of synthesizing the dense products should be developed. In this paper, preparation of full dense Ni₃Al by pressure less combustion synthesis process was investigated.
Some kinds of Ni and Al powders which had different particle sizes were used as initial substances. Ni/Al premixed compacts (Ni:Al=3:1) were made by combinations of the powders. The green compacts were heated in a vacuum furnace, and burned by thermal explosion reaction.
It was found that the dense product was obtained in case of the compact consisted of fine powders. However, a little pore was observed in the product. Accordingly, degassing treatment was introduced during the process, then the nearly full dense product was synthesized. By X-ray and EDX analysis, it was confirmed that the synthesized product became to homogeneous Ni₃Al. Therefore, the combustion synthesis process is effective to compose the Ni₃Al intermetallic compound.

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Powder mixture of Al-40mol% Ni was mechanically alloyed for various milling times. After 72 ks of milling, AINi (β') phase has formed. The crystalline size of AM (β') phase decreases with milling time, and it becomes about 30 nm after 180 ks of milling. When the mechanically alloyed Al-Ni alloy powder was heat-treated at 823 K, the AlNi (β') phase transforms to equilibrium AlNi phase with about 40 nm in crystalline size. The 180 ks milled powders was consolidated by the hot pressing (HP) under various conditions, and structural change of the compacts during the HP was investigated. The microstructure of the compacts consists of equilibrium AlNi phase with about 40 nm of crystalline size. Density of the compacts is increased with the increasing of hot pressing pressure and holding time. Compression tests of the compacts have been carried out to investigate mechanical properties at high temperatures. The intermetallic AINi sample made from the MA powder deforms to high strain under low stress, when compressed at 1073K-1123K for 10^-1s^-1 of initial strain rate. The strain rate sensitivity exponent of yield stress (m-value) reaches to 0.32-0.36 under this compressing condition. Therefore, the ultra fine grained intermetallic AlNi alloy made by the MA and HP process can be formed to near net shapes by superplastic deformation at high strain rate suitable for industrial working.

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The preparation of Sm₂Fe₁₇N_x permanent magnet powders was tried by mechanical grinding (MG) and the subsequent nitriding without crystallization heat treatment which was usually needed to obtain Th₂Zn₁₇ structure in the conventional method by MG or mechanical alloying (MA). MG was carried out in NH₃ gas with a rotary ball mill. The powder after MG for 324ks (90hr) had the sufficient nitrogen content of about 35000ppm. The magnetic properties of this powder, however, was insufficient because of the influence of distortion introduced during MG. In order to decrease the distortion, powders were prepared by MG for short time of 18ks-72ks (5hr-20hr). Although these powders contained an insufficient nitrogen of around 10000ppm, nitriding at 723K for 21.6ks in N₂ raised nitrogen content up to 35000ppm. The powder after MG for 18ks and the subsequent nitriding showed the good rectangularity in the demagnetization curve. From this curve, the saturation magnetization and the remanence were confirmed to be about 1.23Wb⋅m_-2 and 1.06Wb⋅m_-2, respectively.

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The preparation of Sm₂Fe₁₇Nx permanent magnetic powder whose grain size is finer than the single magnetic domain size of about 300nm was tried by MG for short time (3.6-14.4ks) and the subsequent nitriding treatment. MG for 7.2-10.8ks was effective on the absorption of nitrogen during nitriding treatment and the improvement of magnetic properties. The powders prepared by MG for 10.8ks and the subsequent nitriding treatment at 623K for 7.2-10.8ks showed the coercivity higher than 0.96MA/m (12kOe). The grain size of all powders after MG (even MG for 3.6ks) was about 70nm, and this size is sufficiently fine in comparison to the single magnetic domain size. This fine grain size was also maintained even after nitriding treatment.

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RuAl is potentially one of the structural intermetallics with high melting temperature(2333K). We applied mechanical alloying to prepare the intermetallic compounds NiAl and RuAl, which crystal structure are B2 type, using a mixture of elemental Ni, Ru and Al powders. Single phase NiAl have been obtained by ball milling for 75h, while RuAl for 200h. The grain size of NiAl thus obtained was 8.5nm, while RuAl 7nm, that was estimated by the Hall plot. RuAl powder, obtained by mechanical alloying for 400h, was consolidated by Plasma Activated Sintering (PAS) process under the conditions of 50MPa, 1673K and 480sec. Vickers hardness was examined between room temperature and 1373K. RuAl compact obtained by PAS had about two times as high hardness as arc melted RuAl over the whole temperature range measured. Vickers hardness of RuAl compact measured at room temperature was 690Hv and there was no crack around the indentation. The result suggests that RuAl compact had reasonable toughness at room temperature.

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Though the process composed of mechanical alloying, crystallization treatment and nitriding treatment has been used to prepare the Sm₂Fe₁₇N_X permanent magnet powders with high coercivity, the crystallization treatment increases the oxygen content in the specimen.
In this experiment, we tried to prepare the Sm₂Fe₁₇N_X powders by mechanical grinding(MG) and the nitriding treatment at as low temperature as 623K, where two kinds of powders;i.c., hydrogcnetcd Sm_2.5Fe₁₇ powder and non-treated Sm_2.5Fe₁₇ powder, were used as the starting materials, and MG was carried out in three kinds of atmosphere ; i.c., in Ar, N₂ and NH₃ gas.
Though the nitriding was promoted by the existence of hydrogen, the oxidation was also promoted. And it was confirmed that too much hydrogen in the specimen impede nitriding. This phenomenon suggests the existence of the most effective concentration of hydrogen for nitriding. In this work, the nitriding was carried out most effectively on the specimen mechanically ground in NH₃, where the nitrogen content after nitriding treatment was about 38000ppm.

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Mechanical grinding(MG) in Ar and mechanical alloying(MA) in NH₃ have been applied to prepare Sm₂Fe₁₇Nx permanent magnet, where the three diffrent kinds of alloy powders, i.e., Sm₂Fe₁₇, Sm₂Fe₁₇C and Sm₂Fe₁₇C₂ were used as the starting materials. Though Sm₂Fe₁₇ and Sm₂Fe₁₇C specimens obtained by MG or MA were recognized to consist of α-Fe and Sm-Fe amorphous phase, Sm₂Fe₁₇C₂ specimen obtained by MG or MA process was confirmed to consist of only Sm-Fe amorphous phase. The fine grain particles under a single domain size( ?? 260nm) were obtained both by MG and MA, where the powder obtained by MA in NH3 was finer than that obtained by MG in Ar. Nitrogen content of the powder obtained by MA in NH₃, increased as MA time passed. On the contrary, hydrogen content once increased at the first stage of MA, and after that decreased with the increase of MA time.

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Mechanical alloying was applied to prepare the permanent magnets of ThMn₁₂-type NdTM_cFe_12-c nitrides for TM=Cr, Mo, Ti, V. Cr-Mo and Mo-Ti. After isothermal aging and nitrogenation, NdTM_cFe_12-c nitrides were obtained in the alloys of TM=15(at%)Cr, 15Mo, 7.5Cr-7.5Mo, 4Mo-4Ti, 7.5Mo-7.5Ti. Relatively high coercivities of 500 and 45OkA/m were obtained in NdMo₂Fe₁₀N_x and NdCrMoFe₁₀N_x compounds, respectively. Crystal size smaller than 100nm was observed in NdMo₂Fe₁₀N_x powder by TEM and x-ray diffraction. This ultra fine crystal size was considered to be the origin of observed high coercivity.

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The structural development with milling time during mechanical alloying (MA) of Ni and Ti powders with the composition of Ni₇₅Ti₂₅ was investigated by SEM, x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure and hardness of the sintered compacts were studied using x-ray diffraction, SEM, TEM, and vickers hardness tester. Ni solid solution with an amorphous phase was formed in the final alloying stage, which was identified by x-ray diffraction and DSC measurements. The appropriate MA time to obtain a well-sintered compact with respect to the chemical homogeniety, relative density and hardness was found to be longer than 360ks.

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Elemental Powders of Ni and Ti with the composition of Ni₃₃Ti₆₇ were mechanically alloyed for various periods of time by a holizontal ball mill. Changes of shape and phase of the processed powders with processing time were studied using SEM, x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure, relative density and hardness of sintered compacts were studied using SEM, TEN, x-ray diffraction and vickers hardness tester. The existence of an amorphous phase was confirmed as final alloying stage, which was identified by x-ray diffraction and DSC. A single NiTi₂ phase was formed on sintering of well-milled powders. The optimum MA time for sintering with respect to the chemical homogeniety, relative density, and hardness of the sintered compacts was found to be longer than 360ks.

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Mechanical alloying (MA) of elemental Sm and Fe powders in a laboratory ball mill was conducted to prepare Sm₂Fe₁₇N_xpermanent magnet. MA resulted in the formation of an amorphous phase with α-Fe in a wide composition range of Sm-Fe binary system. A single Sm₂Fe₁₇ phase was obtained after the subsequent heating of MA powder of the nominal composition of Sm₁₅Fe₈₅. The MA powder of Sm₁₅Fe₈₅ milled for 360ks was heated at various temperatures in the range 973-1073K and nitrided in an atmosphere of purified N₂ gas flow for various times in the range of 0.3-21.6ks at 703K. It was observed that coercivity depends on both the heating temperature and nitriding time. When the MA powder was nitrided at 703K for 3.6ks, coercivity was observed to be higher as the heating temperature is lower. The coercivity showed a peak with nitriding time and the peak coercivity was obtained with shorter nitriding time as the heating temperature is lower. The effect of MA time on coercivity was studied under the condition of heating temperature 973K and nitriding at 703K for 3.6ks. The coercivity showed a peak with MA time and the largest coercivity was obtained at around 1080ks of MA. The dependence of coercivity on the heating temperature, nitriding condition and MA time was discussed in relation with the powder particle size and the crystal grain size of MA powder.

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Mechanical alloying is applied to prepare Sm₂Fe₁₇N_x permanent magnet. Starting from elemental powders, the formation of hard magnetic phase of Sm₂Fe₁₇N_x by milling in a horizontal ball mill and a successive solid-state reaction was studied. The effect of starting composition of powder on product phase was first investigated. At as milled condition powder was found to consist of α-Fe and Sm-Fe alloy amorphous phases when Sm content is less than 19 at% and consist of α-Fe and SmFe₂ phase when Sm content is 26 at%. After heating and nitriding treatments pow-der was found to consist of α-Fe and Sm₂Fe₁₇N_x when Sm content is less than 15 at% and consist of α-Fe and SmN when the Sm content is 26 at%. When Sm content was 19 at%, nitrided MA powder consists of mostly Sm₂Fe₁₇N_x phase. The effect of milling time was studied for the powder of starting composition of Sm₁₉Fe₈₁. When powder was milled longer than 180ks, almost single phase of Sm₂Fe₁₇N_x was formed after nitriding. Coercivity was observed to increase linearly with logarithm of milling time from around 72ks and reached to 1200kA/m after 360ks of milling. This high value of coercivity was cosidered to be obtained by ultra fine grain size of Sm₂Fe₁₇N_x produced by ball milling and heat treatment.

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Mixture of aluminum, copper and titanium powders was mechanically alloyed and then the powder was heat-treated at various temperature. A change of structure of the powder with milling period was investigated by using XRD, DTA, SEM and EPMA. In the early stage of mechanical alloying, particles of Cu and Ti are deformed and dispersed in Al matrix, but degree of deformation of Ti particle is smaller than that of Cu particle.
Particles of Cu and Ti become finer with the increasing of milling period, and they disperse homogeneously as the milling period reaches to 72.0ks. Intermetallic Al₂Cu phase was observed in the powder mechanically alloyed for 21.6ks. In the powder heattreated at 773K intermetallic Al₃Ti and AlCu phases were observed. The forming temperature of Al₃Ti and AlCu phase decrease with the increasing of milling period.
Intermetallic AlTi phase was observed at low temperature in the powder mechanically alloyed for 72.0ks.

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The structural development with milling time during mechanical alloying (MA) of Al, Ni and Ti powders in the compositions of Al₆₅Ni₁₀Ti₂₅ and Al₂₅Ni₅₀Ti₂₅ was investigated by x-ray diffraction and DSC. The MA powders were sintered by hot press. The phase, microstructure and hardness of the sintered compacts were studied using x-ray diffraction, SEM and vickers hardness tester. An amorphous phase was formed on final alloying stage for both the compositions. The ternary intermetallics of Al_6.5NiTi_2.5(π) and AlNi₂Ti(σ) were confirmed to form on heating the well-milled powders. The optimum MA times for sintering to obtain the chemical homogeniety and enough hardness were found to be longer than 1800ks for Al₆₅Ni₁₀Ti₂₅ and longer than 360ks for Al₂₅Ni₅₀Ti₂₅.

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Elemental powders of Al and Ni with the composition of Al₇₅Ni₂₅ was mechanically alloyed in an Ar gas atmosphere for various periods using a horizontal ball mill. A single phase of disordered AlNi structure (BCC) was obtained by milling of 1800ks. This BCC structure transformed into Al₃Ni compound (DO₂₀) at around 600K. The hot-pressed compacts of MA powders showed compositional inhomogeneity and voids produced by isothermal solidification when powders were milled shorter than 72ks and showed well sintered structure when powders were milled longer than 180ks. The hardness of hot-pressed compacts prepared from MA powders milled between 36ks and 360ks reached at around 750Hv. The suitable MA time for sintering was considered to be between 180ks and 360ks.

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Elemental powders of Al and Ni with the composition of Al₂₅Ni₇₅ was mechanically alloyed in an Ar gas atmosphere for various periods using a horizontal ball mill. A single phase of Ni solid solution with Al super saturation was obtained by a long time milling. This Ni solid solution transformed into AINi₃ compound (Ll₂:ordered FCC) at around 700K with the enthalpy of 4.6kJ/mol. The hardness of hot-pressed compacts prepared from MA powders was higher than that of melted and solidified, irrespective of the MA time. The hot pressed compacts of MA powders showed compositional inhomogeneity when powders were milled shorter than 36ks and showed voids when powders were milled longer than 360ks. The suitable MA time for sintering was in the range between 72 and 180ks.

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Ti_xAl_100-x powders were synthesized by mechanical alloying (MA) of Ti powder and Al powder using a vibrational ball milling in 35kPa Ar. Though MA powders were agglomerated, fine dispersion of Ti and Al elements was performed for 720ksec MA treatment.
Ti-34mass%Al samples, which were prepared by mixing MA powder and Al powder, were hot-pressed at 873K-1173K under 100MPa. The pressing at the melting point of Al enabled 85% deformation of the samples. Furthermore, formation of Ti-Al intermetallic compound was promoted by heating over its melting point. The Ti content in the Ti-Al Intermetallic compound was increased with increasing hot-pressing temperature.

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