Microstructures and mechanical properties of a Cu-bearing ODS steel fabricated by mechanical alloying and hot extrusion

An attractive way to improve the strength of ODS ferritic steels is to develop a Cu-bearing nanostructure. Pre-alloyed powders were prepared through mechanical alloying and consolidated by hot extrusion. After solution treatment, a nanocrystalline structure with a grain size of 200–400 nm is obtained. After aging for 3 h, the microhardness reaches a peak value of HV385, which is attributed to the precipitation of copper-rich phase. The microhardness tends to retain a stable value of HV322 after aging for 60 h. Mechanical properties tests show a much higher strength than Cu-free alloy and bimodal-grained alloy due to the strengthening effect of copper-rich phases and nanograins.