EFFECTS OF Ti ON STRENGTHENING OF ODS FERRITIC ALLOY FOR ADVANCED FBR CLADDING APPLICATION

When an optimum machanical alloying(MA) process was selected, the dispersoids (Y2O3) added in the ferritic alloy will initially dissolve into a matrix during MA, then a kind of super fine complex oxide(Y2Ti2O7) will precipitate during following hot consolidation process By this transition, the dispersoids can be obviously refined from 30 um (Y2O3) to smaller than 10 nm (Y2Ti2O7) and even more uniformly distributed in alloy matrix. It can remarkably enhance the effect of dispersion strengthening and enable the alloy's strength, especially creep strength,to reach a superior high level enough to satisfy the specification of commercial type FBR. But when a high content of Ti (2%) is added in the alloy, X phase can easily precipitate in the alloy's matrix during aging the alloy at 800℃ for 24 h, which can not contribute to 650℃ tensile strength, and is very harmful to tensile ductility and creep strength of the alloy.