It is well known that sintered manganese steel has a good mechanical property, but the sintering is believed not easy due to the fact that oxide of manganese is not readily reduced.
First, the physical and mechanical properties of sintered iron-manganese alloys were studied. The results obtained were as follows :
(1) A maximum tensile strength of about 44kg/mm² can be obtained for the sintered ironmanganese alloys (no carbon content).
(2) Tensile strength, transverse rupture strength and hardness increase with an increase in an amount of manganese, with their maximum value for 10 wt. % manganese.
(3) In order to obtain good mechanical properties, it is necessary to sinter the compact from ferro-manganese alloy powder or at a sintering temperature of 1300°C.
(4) With the higher densities of compacts made from high manganese additions, it is expected to obtain an alloy having reasonably high tensile strength and ductility.

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The annealing characteristics of the pure coppers and the dispersion strengthend copper alloy were compared. The dispersion alloys were prepared by ballmill-mixing electrolytic copper powder (-325 mesh) with thoria, alumina or tungsten powder up to 3.0 volume percent, followed by compacting, sintering, hot extruding and cold drawing. The three kinds of pure coppers were used for comparison to the dispersion strengthened alloys-1st produced from vacuum melted cathode copper, 2nd from sintered copper powder and 3rd from vacuum melted copper powder. The specimens cold to drawn 1.6mm in diameter were annealed at temperature up to 1050°C for 2hr in vacuum.
The properties of annealed pure coppers were affected by the impurity concentration. The purity of electrolytic copper powder was worse than that of cathode copper. On annealing at temperature above the recrystallization temperature, the grain size of pure copper produced from cathode copper became larger with an increase in annealing temperature and the mechanical properties were lower. In the case of copper specimens produced from copper powder, the marked change of the grain size and of the mechanical properties did not occur until the annealing temperature reached at the 2nd recrystallization temperature, which was about 800°C. When these specimens were annealed at temperature above 800°C, the very coarse grains appeared and the mechanical properties were much poorer and the electric resistance was higher than as drawn.
However, in the case of the dispersion strengthened alloys containing a dispersed phase of 3.0 volume percent, it was shown that even though annealed at 1050°C the marked grain growth of matrix did not occur, and the mechanical properties and the electric resistance also showed the same value as that annealed at 600°C. Among the three dispersion strengthened alloys, the alloy containing thoria had the most excellent mechanical properties and high temperature stability.

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Atomization appeared to be the best means of obtaining pre-alloved powders without applying a limitation on composition. However, difficulty in the control of particle shapes has restricted the utilization of pre-alloyed powders produced by that process. The investigation has been therefore made on the water atomization of copper alloys, and subsequently the physical properties of the powders and of their pressed compacts were examined.
The results were summarised as follows : -
(1) Molten copper alloys atomized with water become the irregular particles, and this leads to be low apparent density.
(2) To facilitate to produce compacts of high green strength, it may be necessary for atomized bronze and brass powders to be annealed at an adequate temperature.
(3) High rate of cooling velocity developes quenched phase structure in alloys, particularly with alloys such as bronze and Kelmet that has a considerable gap between the liquidus and the solidus. Particles atomized with water show fine quenched phase structures, in comparison with the particles atomized with gas.

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