Enhanced strength-ductility combination in IN718 by coherent yttrium oxides dispersion strengthening

Further enhancing the performance of oxide dispersion strengthening (ODS) IN718 superalloy and overcoming the stress concentration induced by heterogeneous oxide particles remain key challenges. In this study, IN718 superalloys with uniformly dispersed oxides were prepared by arc consumable remelting. These oxides form coherent interfaces with both the γ matrix and the γ″ precipitates, thereby achieving simultaneous improvements in both strength and ductility. The yield strength of the ODS IN718 increased by 7.6% at 650 °C and 17.2% at 700 °C, while the elongation after fracture was enhanced by approximately 100% and 101%, respectively. These improvements stem from the heterogeneous nucleation of γ″/γ′ at the dispersed yttrium oxides during aging, which refines their distribution and spacing, thereby strengthening dislocation pinning. Moreover, yttrium oxides inhibit grain boundary migration and stabilize grain size during hot deformation. The composite precipitates of γ″ and yttrium oxides also suppress dislocation climb and reduce dynamic recovery, limiting sub-grain formation. The increased stored deformation energy and dislocation reactions promote a deformation mechanism dominated by primary and secondary deformation twinning, ultimately enhancing uniform deformation capability.