γ′ Precipitation and Growth Kinetics in Mechanically Alloyed Ni-Al

Abstract

The precipitation and growth kinetics of γ′ precipitates, which are strengthening factors in Ni-base oxide dispersion strengthened (ODS) superalloys, were investigated. The cuboidal-type γ′ precipitates are formed in conventional arc-melted Ni-Al alloys, whereas spherical-type precipitates are formed in the mechanically alloyed (MAed) specimens. The morphology is controlled by a lattice misfit between the γ′ precipitates and the matrix at the aging temperature of 800γ′C. The growth kinetics of the γ′ precipitates can be followed by Ostwald ripening. The Arrhenius plot yielded a lower activation energy for the solute atom diffusion in MAed specimens, which is attributed to their high dislocation density and nanosized grains. Copyright © 2011 QingXin Tang et al.