Static tensile properties of HIP'ed Ti-Co binary alloys containing 2 wt% or 4wt%Co were studied, and metallographic and fractographic observation were also carried out by scanning electron microscope and X-ray energy dispersion analysis.
Despite the low level of oxygen content, the HIP'ed specimen using Hunter process sponge fines as titanium source, showed poorer ductility properties than the HIP'ed specimen using hydride-dehidride Kroll process sponge fines of high oxygen content as titanium source, and it was confirmed that the above mentioned ductility degradation was closely related to the existing NaCl in the HIP'ed specimen using Hunter process sponge fines. Brittle fracture was observed in a part of the specimen using Hunter process sponge fines, which is also considered to be due to the above mentioned NaCl existing in the HIP'ed specimen using Hunter process sponge fines.

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Mechanical properties of Fe-Ni-P alloys sintered by using atomized iron powder electroless plated with nickel-phosphorus alloy were studied. The sintered alloys with plated powder showed higher tensile strength and larger elongation than those of sintered alloys with mixed powders. The microstructure of the sintered alloys showed a composite structure consisted of two regions. The one is the intergranular region contained smaller iron particles, where nickel content is higher, forming a kind of skeleton in the sintered alloy. The other is the inside region of larger iron particles where iron remains low alloyed after sintering. This composite structure gives the high tensile strength and the large ductility of Fe-Ni-P alloys sintered with plated powder. The relationship between the tensile strength and the content of nickel and phosphorous (in mass%) of sintered Fe-Ni-P alloys with plated powder was represented by the following empirical equation.
σ=24.2(Ni+10P)+218 [MPa]

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Silicon nitride ceramics were implanted with 200 KeV Cr⁺ ions and then oxidized at temperatures from 1273 to 1473 K in air. The oxidation scales were examined by RBS, XRD and SEM methods. At temperatures up to 1373 K, in the Cr₊-implanted ceramics, the implanted Cr atoms were predominantly oxidized to Cr₂O₃, which resulted in a reduction of the oxidation of Si₄N₄ to SiO₂, and then the diffusion of impurity cations through the grain boundary to the surface oxide (SiO₂) was also retarded. For the oxidation at 1473 K, there was little difference in oxidation behavior between the implanted specimen and the unimplanted one. But the preoxidation at 1273 K of the implanted specimen was found to give the implanted specimen a little better resistivity against the oxidation at 1473 K.

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The Si₃N₄-(0-24) mol%Y₂O₃-(0-27) mol%ZrO₂-(4.0-4.6) mol%Al₂O₃ compacts were sintered under 0.5 MPa of nitrogen gas at 2073 K for 7.2 ks. The room temperature mechanical properties such as transverse-rupture strength (σ_m), fracture toughness (K_IC) and hardness (H_V) and the microstructure of the compacts were investigated.
It was found that the compact showed high strength of about 0.7 MPa in the composition range of low Y₂O₃, low-high ZrO₂ or low-medium Y₂O₃+ZrO₂ contents, and it showed low strength of about 0.3-0.5 GPa in the other composition range. The dependences of both K_IC and H_V on the composition were nearly the same as am. The low values of the mechanical properties in the above composition range could mainly be attributed to the appearance of the soft grain boundary phases such as Y₂SiO₅, Y₂₀N₄Si₁₂O₄₈, etc., and also to the largeness of the domain of those grain boundary phases.

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Some properties of a TiC-20 vol%TiN-7 vol%Mo₂C-8 vol%Ni alloy with addition carbides of TaC, NbC or WC, such as microstructure, mechanical properties in the temperature range from room temperature to 1273 K, resistance to oxidation at 1273 K, cutting performance for SNCM439 steel, etc., were investigated. Among the results obtained, those of the alloy having additional WC were considered to be of great interest. It was noted that, with increasing the amount of additional WC, the carbonitride structure became especially fine, and in spite of the fine structure, high temperature hardness and cutting performance were highly improved. The discussion on the phenomenon was in detail given.

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By utilizing the excellent properties of a boride, a new type of sintered hard alloy has been developed. This alloy, categorized as a cermet, is produced by liquid phase sintering and comprises a M₂B (M: metal) boride as a hard phase and a ferrous binder phase containing Cr, Ni and other alloying elements.
In the present investigation, the sintering phenomena of Fe-(4-8) wt%B-(0-30) wt%Cr-0.3 wt%C alloys are studied by means of TG-DTA, dilatometric measurements and x-ray diffractometry. In addition, the mechanical properties of the sintered alloys are discussed.
The results can be summarized as follows:
(1) The hard alloy comprises an Fe₂B type boride as a hard phase and a ferrous binder phase containing Cr and C. When the hard alloy contains more than 10 wt% Cr, both Fe₂B and Cr₂B type borides coexist.
(2) The liquid phase sintering of the alloy is attained by two liquid forming reactions, namely, γ-Fe +Fe₃ (B, C)+M₂₃(B, C)6 L₁ and γ-Fe+Fe₂B L₂, the latter reaction occurring in a higher temperature range.

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