| As the most common materials,steel is widely used in buildings,transportation,chemical and other fields.As a kind of steel material,martensitic stainless steel is characterized by good hardenability.It can be strengthened by numerous heat treatments and deformation processes,e.g.,quenching,tempering and rolling.Therefore,martensitic stainless steel is widely used in engine blades,bearings,cutting tools,large castings of hydropower stations and valve castings.The conventional martensitic stainless steel is usually quenched to obtain ultra-high hardnessdue to martensitic transformation,but at the cost of ductility.Nowadays,the reqirements of ultra-high strength,good corrosion resistance,structural weight reduction and low cost in many application fields make the high-strength martensitic stainless steels attractive in the steels community.It is necessary to explore methods ultilizing combined heat treatments and deformation techniques to obtain super high strength and sustained ductility.AISI420 steel was selected in this paper,and the ultra-high strength ferrite(F)-martensitic(M)duplex stainless steel and ultra-high strength martensitic stainless steel were prepared by the processing route combined heat treatment and plastic deformation.Microstructure evolution,mechanical properties and toughening mechanism of the high-strength stainless steels were studied.The main contents of this work are as follows:(1)A novel processing route for preparing ultra-high strength F-M duplex stainless steel was proposed,which was realized by warm rolling on the quenched duplex stainless steel.The tensile strength of the prepared F-M duplex stainless steel reaches up to 2395 MPa and the total elongation is 5.09%.The excellent mechanical properties are mainly attributed to the high density of dislocations introduced by warm rolling,the nanostructure stabilized by the carbides which can implede dislocation motion and boundary slide.(2)A processing route for preparing ultra-high strength martensitic stainless steel is proposed.The process was mainly realized by warm rolling on the quenched full martensitic stainless steel.The tensile strength of the prepared full martensitic stainless steel reaches up to2448 MPa and the total elongation is 8.06%.In addition,the effects of tempering,warm rolling and tempering & cold rolling on the microstructure and mechanical properties of martensitic stainless steel were studied.(3)Martensitic stainless steels with improved strength,ductility and corrosion resistance were produced by quenching at 1100 °C and tempering at different temperatures.The effects of the tempering temperatures on the microstructure,mechanical properties and corrosion properties of AISI420 steel were studied.Moreover,the influences of tempering,phase composition and plastic deformation on the corrosion performance of 420 stainless steel were studied in depth. |
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