Preparation and Properties of Oxide Dispersion Strengthened Ni Powders by the Application of Mechanical Alloying Method

Abstract

Oxide dispersion strengthened nickel powders containing fine Al₂O₃, ZrO₂ or Y₂O₃ particles as the dispersoids were prepared by mechanical alloying of carbonyl nickel powders with Al-, Zr- or Y-alkoxide in the air atmosphere followed by heat-treatment in a hydrogen atmosphere at 600°C. The powders thus obtained were then consolidated by compacting and sintering at temperatures from 600°C to 1200°C in a hydrogen atmosphere. Results obtained were as follows:
1) The microstructure of each powder obtained was very fine, and the crystallite sizes of them were in the range of 35nm to 71nm.
2) Among these powders, only Ni-Al₂O₃ powder showed superior sinterability. The 0.2% -bending strength of the specimen obtained by sintering this powder at 1200°C was 870MPa, which was more than eight times as high as that of the specimen obtained by sintering pure nickel powder.
3) In the case of Ni-Al₂O₃ powder, sintering began to proceed rapidly in the temperature region where losing the coherency between matrix and Al₂O₃ particles were significant.