Characterization of Nanoscale Clusters in Ods Iron-Based Alloys

Abstract

The high temperature application of iron-based ferritic alloys is limited by their rapid decrease of yield strength at temperatures approaching 1000°C. It has been shown that mechanical-alloying (MA) to produce oxide dispersion-strengthened (ODS) ferritic alloys improves their high temperature mechanical properties. Prior characterization of such materials has shown that in certain as-processed alloys the original yttria oxide particles are replaced by nanoscale (2-5 nm diameter) clusters containing Ti, Y and O. As a result of the high density of these fine clusters, dislocation pinning produced a ∼10-fold increase in dislocation density relative to similar ODS materials not exhibiting the nanoscale clustering. The improved creep resistance of the clustered material was attributed both to the higher dislocation density, additional dislocation pinning and resistance to recovery during creep. The current work examines clustering in a related alloy, as well as the effects of high temperature creep on the stability of such clusters.