Manufacturing and Microstructural Evolution of Mechanuically Alloyed Oxide Dispersion Strengthened Superalloys

Abstract

Mechanical alloying is a process in which mixtures of powders are severely deformed until they form atomic solutions. Inert oxides can also be introduced to form a dispersion of fine particles which help strengthen the consolidated product. Significant quantities of iron and nickel-base alloys, with unusual properties, are produced commercially using this process. The total true strain during mechanical alloying can be as large as 9; there is proof that this leads to mixing on an atomic scale and to the development of a uniform grain structure which is sub-micrometer in size. Following mechanical alloying, the particles are consolidated using standard powder metallurgical techniques. The consolidated metal has a large stored energy, approaching 1 J g–1. This ought to make it easy to induce recrystallisation, but in practice the alloys fail to recrystallise except at very high temperatures close to melting. On the other hand, the recrystallisation temperature can be reduced dramatically by slightly deforming the consolidated product prior to heat treatment. It is in this context that the solution formation, microstructure and mechanical properties of such alloys are reviewed here.