Using mixed powder compacts of Fe-Ni-1.0 wt%C system with different Ni contents and Fe-4.0wt%Ni-C system with different graphite contents, the influence of Ni addition on the carburization and the dimensional changes were investigated by means of the differential dilatometric method and carbon analysis.
The results obtained are summarised as follows:
(1) Carbon content combined during heating process up to 900°C, which is about 0.1 wt% in a Fe-1.0 wt%C binary compact, increases with increasing Ni content in Fe-Ni-1.0 wt%C ternary compacts.
(2) In the case of the ternary compacts which content carbonyl Ni powder, the sintering rate is remarkably promoted. Also the sintering promotive effect is observed in Fe-carbonyl Ni-1.0 wt%C compacts. These results suggest that the shrinkage due to the sintering of fine powders plays an important role in the promotion of sintering.
(3) The combined carbon concentration of the Fe-1.0 wt%C binary sintered compact is nearly the same as that of eutectoid composition. However in Fe-Ni-1.0 wt%C ternary sintered compacts, some hypereutectoid regions are observed, because the carbon concentration lowers with increasing Ni content along the Fe-Ni-C ternary eutectoid line. Therefore the retained shrinkage increase remarkably by the contraction due to the precipitation of primary cementite in the Ni content more than 6 wt%Ni.

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We examined some structural characters of Fe-Ni-C ternary sintered compacts on the basis of the diffusion-experimental results of (Fe-C)-Ni diffusion couple, and also investigated the mechanical properties of Fe-(0-10) wt%Ni-(0-1.0) wt%C ternary sintered compacts.
The results obtained are as follows:
(1) In Fe-Ni-C ternary mixed powder compacts, sintering is promoted with increasing Ni and grahite contents.
(2) An unhomogeneous structure is observed in Fe-Ni-C compacts sintered at 1150°C for 60 min, and this structure may be mainly controlled by the distribution of Ni.
(3) The Ni and graphite concentrations showing the maximum strength in the sintering condition at 1150°C for 60 min are approximately 10 wt% and 0.6 wt% respectively, and it is confirmed from the microstructure that a higher content of martensite is observed in the composition and austenite is scarcely observed.

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This investigation is carried out to examine the influence of compacting and sintering conditions on internal friction of sintered iron materials as compared with the density and the tensile strength. The results are as follows. Internal friction becomes small with the increase of compacting pressure, because the density be comes large. δ of the material sintered at temperature higher than 1000°C is expressed by δ=3.4 × 10²ρ^-2.7T^-1, where ρ the density (g/cm³) and T the sintering temperature (°C). Internal friction also becomes small with the increase of sintering time, because the density and the grain size become large. Internal friction of sintered material in nitrogen gas is small as compared with that of sintered material in vacuum or hydrogen gas. Internal friction becomes small as copper or nickel powder is added to iron powder.

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The effects of the addition of carbides such as VC, Cr₃C₂, NbC, TaC and WC on the strength of TiC-Mo₂C base cermets were studied at room temperature, considering the kind of binder phase, i.e., Ni and Co. Volume percents of Mo₂C, added carbide and binder phase were 13.9, 10.0, and 13.4 respectively.
It was found that the Co-bonded cermets showed generally higher σo and hardness than the Ni-bonded cermets, and the highest values of σo and hardness were obtained in the case where WC (or TaC) was added to the former cermets; here σo is the intrinsic strength of the alloy having no microstructural defects. However, the transverse-rupture strength of Co-bonded cermet with WC (or TaC) was found to be smaller than that of the commonly used Ni-bonded cermet having no additional carbide. The reason was discussed in some detail.

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The transverse-rupture strength (σm) of TiC-20%Mo₂C-20%Ni(Co) and TiC-20%Mo₂C-15%TiN-20%Ni(Co) cermets were studied in the temperature range from 600 to 1000°C; attention was paid to the fracture source. The σm of WC-8%Co alloy having the same volume fraction of binder phase was also studied for comparison.
The results obtained were as follows: the Co-bonded cermets generally showed higher σm than Ni-bonded cermets above about 600°C, and the TiN-free cermets showed higher σm than TiN-bearing cermets above 800-900°C. The strength decrease of cermets with rising temperature was gradual up to 600-800°C. but became sharp above 800-900°C. The latter temperature range of 800-900°C was higher than that of WC-Co alloy, resulting in the higher σm of cermets than WC-Co alloy above about 900°C. These results were discussed in close relation to the fracture source which varied in type and dimension with variation of test temperatures.

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Magnetic properties of Fe-Be compounds were studied. The highest value of both magnetization and Curie temperature was observed at the composition of FeBe₂. Intensity of magnetization of these compounds suggests that each of Fe atom has different magnetic moment, which depends on the condition of their nearest neighbour atoms. Coercive force of I kOe and magnetization 4πM_s of 7 kG/cm³ were obtained for a powder sample of FeBe₂ with mean diameter of 1 μm.

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