Effects of milling parameters on the microstructure and Charpy impact properties of MA/ODS ferritic steels

ODS ferritic steels were produced by mechanical alloying (MA) in either attritor or planetary ball mills under argon atmosphere and hot extrusion. Milling in argon with controlling excess oxygen (Ex.O) and nitrogen was effective to reduce the particle size of MA powders. Coarse Al2O3 particles and fine AlN precipitates were found to be formed in an Al added steel when the Ex.O and nitrogen concentrations are increased. Lowering the Ex.O and nitrogen concentrations in ODS ferritic steels acted as a key parameter for enhancing their impact properties.