Solid-solution strengthening by Al and Cr in FeCrAl oxide-dispersion-strengthened alloys

Abstract FeCrAl oxide-dispersion-strengthened (ODS) alloys are promising materials for accident tolerant fuels for light water reactors (LWRs). In these alloys, Al and Cr are key elements with important synergistic effects: enhancement of the formation of oxidation-resistant Al2O3 phase by Cr addition and suppression of the formation of the embrittling Cr-rich α′ phase by Al addition. The solid-solution strengthening resulting from Al and Cr co-addition was investigated in this study. The Al and Cr contents were systematically varied from 9 to 16 at.% and 10–17 at.%, respectively, and tensile tests were conducted at 298 K, 573 K, and 973 K. The solid-solution strengthening increased linearly, 20 MPa per 1 at.% Al and 5 MPa per 1 at.% Cr, at the typical LWR operational temperature of 573 K. The conventional Fleischer–Friedel and Labusch theories cannot explain this level of solid-solution strengthening. It was originally clarified that the solid-solution strengthening by Al and Cr in the FeCrAl-ODS alloys can be reasonably predicted by modifying shear modulus difference for the Suzuki's double kink theory for screw dislocations. The inverse dependency on the absolute temperature and linear dependency on the Al and Cr content can be successfully realized by this approach.