Design and synthesis of an oxide-dispersion-strengthened (ODS) steel by laser additive manufacturing
LAM involves rapid melting and solidification with only a small melt pool volume existing at any time during the manufacturing process. This offers the opportunity to manufacture materials that cannot be cast conventionally, e.g. oxide-dispersion strengthened alloys.
Typical cooling rates encountered in LAM range from 103 to 108 Ks-1. Such high cooling rates lead to rapid solidification of the melt, yielding beneficial, very fine solidification microstructures, in contrast to the usually coarse casting microstructures obtained after the first step of conventional processing. Essentially, the melt pool in LAM is the equivalent of the crucible in conventional casting: alloying, solidification and other reactions such as precipitation occur on a local scale.
The combination of high cooling rates and local metallurgy enables synthesis of materials that are not accessible by conventional casting. Rapid solidification allows quenching-in of microstructures that are far from thermodynamic equilibrium, e.g. supersaturated solid solutions or even metallic glasses. Small melt pools together with strong Maragnoni convection induced by the laser beam allow depositing homogeneous particle-reinforced materials that cannot be produced by conventional casting due to segregation or immiscibility effects and must nowadays be produced through the conventional powder metallurgy route which is time and cost consuming
In this project, we are working on the development and manufacturing of a novel oxide-dispersion strengthened (ODS) steel processed by LAM without the need for time-consuming and costly prior mechanical alloying. We are exploiting the local metallurgy characteristics of LAM, i.e. high cooling rates in liquid and solid, strong convection and small melt pools as well as its rapid alloy prototyping capabilities to produce a material which is inaccessible by conventional liquid metallurgy, but which has highly desirable (high temperature) mechanical properties.