New dispersion mechanism for oxide dispersion-strengthened steels by liquid metallurgy

Abstract

The use of oxide dispersion-strengthened (ODS) alloys in demanding applications can effectively reduce parts’ weights, extend life of use, and enhance overall energy efficiency. But, the current manufacturing of ODS alloys has remained impractical for decades due to poor scalability and extremely high costs. Mass production of ODS steels by liquid metallurgy is therefore crucial to decrease their costs by several orders of magnitude and expand their potential applications. However, oxide nanoparticle (NP) dispersion in molten alloys presents fundamental challenges for liquid metallurgy due to the vastly dissimilar atomic properties between ionocovalent oxides and metals. Here we show, for the first time, that Y2O3 NPs are able to be dispersed in liquid 316L with a 1 % Nb addition. It was discovered that Nb-enriched interfacial layers exist around the Y2O3 NPs in solidified steels after slow cooling. Theoretical analyses reveal that the Nb-enriched interfacial layer induces a higher energy barrier and a significantly lower van der Waals attraction between oxide NPs and liquid Fe for the successful dispersion of oxide NPs in liquid steels. Moreover, Y2O3 and Al2O3 NPs were successfully dispersed in lean steels, such as Fe-Nb and low-C steels. This new dispersion mechanism of oxide NPs opens an exciting pathway for the economical mass manufacturing of various ODS alloys by liquid metallurgy for numerous applications.