Influence of consolidation methods on the recrystallization kinetics of a Fe–14Cr based ODS steel

Abstract

The recrystallization behavior during thermal annealing with or without prior cold work has been investigated in a 14%Cr ODS steel consolidated by two different methods, hot extrusion (HE) and hot isostatic pressing (HIP).We show that a 1400°C-1 h annealing induces an increase of the oxide nanoparticles radius from 1.3 to 3 nm, however the grain size remain stable despite a recovery of sub-grain boundaries for the hot extruded material.When pre-deformation is applied before annealing, almost full recrystallization can be achieved on the HE ODS steel. In this study, we show recrystallization after 40% cold deformation and annealing 30 min at 1450 °C together with coarsening of oxide particles. At lower temperature and higher pre-deformation (70%-1150 °C/30 min), we show that recrystallization can be achieved without change of the oxide size distribution.We show that due to a lower initial dislocation density, recrystallization is strongly delayed, by at least 250 °C, in the HIP material. Finally, we show that the evolution of the size of the oxide precipitates is controlled by the time and temperature of annealing and are independent on the pre-deformation and occurrence of recrystallization.