Effects of Ti addition on microstructure and mechanical property of spark-plasma-sintered transformable 9Cr-ODS steels

By adding Ti consistent, dual-phase 9Cr ODS steel with martensite and transformed ferrite is fabricated by spark plasma sintering, and M23C6 carbides are identified in transformed ferrite. Although Ti is strong carbide forming element, Ti concentration has a negligible effect on the distribution of M23C6 within ferrite, as well as martensite size. With Ti addition increasing, the amount of ferrite is increased, and more fine Y-Ti-O complex oxides are produced. Annealing treatment will not change the ferrite distribution, but the density and size of oxide nanoparticles in steels will be affected. It is found that Ti addition can effectively improve the tensile strength of 9Cr ODS steels, which is related to the Y-Ti-O oxides with small size. The large-sized ferrite grains will induce ductile-brittle mixed fracture, deteriorating the ductility of transformable 9Cr ODS steels.