Relations between granular structure and magnetic properties of Mn-Zn ferrite are presented. In order to obtain ferrite specimens with different granular structures in the same chemical composition, four powder samples having different grain growth characteristics were prepared from the same raw material mixture under the different calcining and ball-milling conditions, and their compacts were fired under the same temperature.
It is shown that under the conditions studied flux density is determined by the fired density irrespective of the granular structure, but that initial permeability, coercive force and quality factor have much to do with granular structure. It is shown also that the grain size has little effect on the magnetic properties. It is stressed, however, that the intergranular pores are highly responsible for the degradation of magnetic properties.

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Investigations were made on some fundamental properties of WC-10%(Co-Ni) alloys affected by the carbon content, i.e., the composition of binder phase in the alloys. Specimens were sintered in vacuum at 1375°C for 1.5 hr. Main results obtained were as follows :
(1) The composition of binder phase in the alloys showed a marked change in the two phase region as in the cases of WC-Co, WC-Ni alloys, etc., i.e., the amount of tungsten dissolved in binder phase increased sharply with decreasing carbon content and increased also with increasing nickel content in binder phase.
(2) Therefore, the properties of the alloys lie between those of WC-Co and WC-Ni alloys, as well as they showed regular changes similar to those in other WC-Co base alloys. It is suggested that the mechanical properties of the alloys containing up to about 10% of nickel in binder are nearly the same as those of WC-Co alloys.
(3) With increasing nickel content, the two phase region of the alloys shifted towards the lower carbon side with the extension of that phase region.
(4) Summerizing, the WC-(Co-Ni) alloys were confirmed to situate between WC-Co and WC-Ni alloys.

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It is useful to observe the structure of brush material and to measure its hardness, in order to get several informations on the distribution of raw material and its heat treatment condition.
We report in this paper the structure and their hardness of brushes used for the rolling stock of J.N.R. These brushes were polished with electrolytic polisher and the surfaces were observed microscopically. Their hardness were measured by several hardness testers.

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