Abstract
Three methods are described for the preparation of a stable oxide in copper, nickel, or iron. The first, which has been applied to all three metals, requires a reaction between the matrix metal oxide and the refractory oxide at high temperatures such that subsequent reduction will yield a dispersion of oxide in the matrix metal powder. In the second method, copper hydroxide or carbonate is precipitated in the presence of an aluminium salt. Ignition of the precipitate to the oxide followed by hydrogen reduction gives a copper powder containing a dispersion of alumina. In the third process, a salt that can be decomposed to a stable oxide is dissolved in molten nickel nitrate, which on rapid cooling eitherretains the additive in solid solution or as an intimate dispersion. Nickel powder containing the dispersed oxide is obtained on subsequent decomposition.
The results on sintered and worked materials show a substantial improvement in mechanical properties compared with the pure metals. Improvements are also achieved in the sintered nickel alloys, which can be sintered to high densities. The effect of the dispersion on the structure and recrystallization behaviour of these materials is discussed.
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