A comparison has been made between the recrystallization behaviour of the same composition copper plates fabricated from the ingots of cast metal and powder-metallurgy metal.
Using the hardness and X-ray analysis combined with metallographic studies, it has been shown that
the two materials recrystallize in different manners. In primary recry-stallization, at cold reduction less than 50 per cent, powder-metallurgy copper recrystal-lized at lower temperature than cast metal. While, more than 50 per cent, powder-meta-llurgy metal recrystallized at higher temperature than cast metal. Therefore, powder-meta-llurgy metal exhibits good resistance to softening in heavy working. In secondary recrystallization, cast copper began coarsening at lower temperature than powder-metal-lurgy metal, but, after completion of secondary recrystallization, powder-metallurgy metal presented larger grain than cast metal.
In relatively porous specimen, powder-metallurgy metal exhibited normal, continuous and slight grain growth without secondary recrystallization.

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In the 1st. report, the effect of carburization temperature, carburization time, the specific surface area of W powder, CH₄/H₂ ratio in volume, and the thickness of W powder on the carburization of W powder by H₂-CH₄ mixture has been discussed. In this paper, the effect of heating of imperfectly carburized W powder at lower temperatures for 30 min in the temperature range of 1200°C-1400°C in a stream of H₂ and H₂-CH₄ mixture have been studied and the change of lattice constants of residual W with progress fo carburization has been studied. The mechanism of carburization of W powder by H₂-CH₄ mixture has been also discussed. The results obtained are summarized as follows: (1) The lattice constant of the residual W in gaseously carburized powder is smaller than that of normal W and approaches to normal value with progress of carburization. (2) By heating at higher temperatures the diffracted X-ray of WC in carburized powder becomes sharper. (3) When WC powder which is carburized at lower temperature, is used in popuration of WC-Co alloy, abnormaly grown grains appear and the number of these grains increases with the broadening of the diffracted X-ray of the used WC.

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The effect of MgO additive to the sintering of very fine a-A1203 was discussed in this experiment. The continuous shrinkage during sintering was observed in the special high temperature dilatometer, and the grain size of sintered compact was obtained from the electron micrograph.
The investigation shows :
1) The temperature at which the shrinkage begins, supposedly it is nearly equal to the initiation of the sintering, was slightly lowered by the MgO addition. This was found about 900-1000°C, the same at which the spinel formation between Al₂O₃-MgO occured.
2) The shrinkage increased by adding MgO, while the timerate of shrinkage at isothe-rmal holding was found to become decreased.
3) The increased grain growth was observed by the addition of MgO. And, the higher the sintering temperature, the greater the effectiveness of MgO addition.
By these three observations, the accelerating effectiveness of MgO to the sintering of Al₂O₃ was confirmed experimentally.

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