Effects of Zr Content on the Microstructure of FeCrAl ODS Steels

Abstract

FeCrAl oxide dispersion strengthened (ODS) steels are an important kind of cladding material for accident-tolerant fuels. Their radiation resistance and mechanical properties are closely related to the grain size and dispersed second phases. In order to tailor the microstructure and provide an experimental basis for the composition design of FeCrAl ODS steels, in this paper FeCrAl ODS steels with different Zr contents were prepared by mechanical alloying and the subsequent hot isostatic pressing (MA-HIP) process. The effects of Zr content on the grain size distribution and the precipitation of dispersed second phases in FeCrAl ODS steels were investigated by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). The results showed that the grain size decreased first and then increased as the Zr content increased, and that the average grain size achieved the minimum value of 2.092 μm when the Zr content was 0.6 wt.%. The Zr content had a negligible effect on the grain orientation of FeCrAl ODS steels, but the dispersed second phase changed from the Al2Y4O9 phase with monoclinic structure to the Y4Zr3O12 phase with hexagonal structure as the Zr content increased.

Keywords

• FeCrAl ODS steels
• Zr addition
• grain size
• second phases