The effect of chemical composition and heat parameter on Nano-sized precipitate dispersion characterization in ODS steels

Abstract

Oxide dispersion strengthened (ODS) supersaturated solid solution alloy powders with different Y/Ti atomic ratios were formed by mechanical alloying (MA) method and then heat treated under different conditions. The morphology, phase composition, and particle size distribution were researched. The precipitate distribution densities and hardness values of alloy powders after heat treatment were measured at the same time by the SAXS method and hard tester. The results show that the morphology of MA alloy powders is irregular in shape and only a small amount of MA alloy powders is bigger than 30 μm. During the MA process, alloy elements are solid solutions in the matrix. The work-harden effect of alloy powders formed in the MA process would be eliminated during the heat treatment process. The chemical composition and heat treatment parameters are crucial effects on nano-sized precipitate distribution characterization in ODS steels. The ODS sample with a Y/Ti atomic ratio of 0.99 has the highest distribution density of oxide precipitates at 1.89×1022/m3 resulting in the highest hardness value during the heat treatment process. The sample with a Y/Ti atomic ratio of 0.42 has the highest distribution density of nanoclusters 7.32×1023/m3.