| Oxide dispersion strengthened(ODS)steel are considered as important candidate materials for the generation VI fission reactor fuel cladding.Their grains are uniformly dispersed with high-density nano-sized oxides and ODS steels have micron and nano-scale grains.These unique microstructures make ODS steel have excellent high-temperature performance and radiation resistance.In present study,the relatively mature preparation technology of ODS steel was powder metallurgy technology,through mechanical alloying and hot isostatic pressing sintering.The finished product of nuclear reactor fuel cladding prepared from the blank will undergo plastic deformation by hot processing technology.In order to explore the influence of hot rolling technology on microstructure,dispersion phase and mechanical properties of ODS steel,in this paper,ODS steel of Fe12Cr2W0.3Y and Fe12Cr2W4.5Al two systems(hereinafter referred to as FeCrWY and FeCrWAl series)were selected to prepared by hot isostatic pressing method to finish hot rolling in the form of wedge plate at 1100 ~oC,adopts high flux experimental design scheme,and uses wedge plate samples to obtain multiple deformation quantities at one time.In this paper,the microstructure,microstructure and dispersion phase of the initial sample and hot rolled sample are studied:phase identification is carried out on the initial sample and the sample with the maximum deformation(70%).The microstructure of samples with different compositions and different deformation amounts were observed,the microstructure changes before and after hot rolling were analyzed,and the composition,size and distribution of dispersed phase were analyzed.The high temperature mechanical properties of samples with different compositions and different deformation amounts were investigated,and the following conclusions were obtained:(1)After hot rolling,the FeCrWY series plates added with Y2O3 have cracks,while FeCrWAl series plates have no obvious cracks,and have good hot working deformation capability.(2)FeCrWY series samples prepared by hot isostatic pressing undergo martensitic transformation after rolling,changing from ferritic steel to ferritic/martensitic dual phase steel.FeCrWAl series samples did not undergo phase transformation after rolling and were still ferritic steel with excellent high temperature stability.(3)The FeCrWY/FeCrWAl series samples prepared by hot isostatic pressing are all equiaxed ferrite grains.After hot rolling,the grains are elongated along the rolling direction.After hot rolling,the average grain size of FeCrWY samples decreases while that of samples added with Y2O3 increases slightly.However,the ND grain size of FeCrWAl series samples is obviously refined.The grains of the samples before and after hot rolling have no obvious preferred orientation,and the orientation tends to be randomly distributed.Local strain is located in martensite region and fine grain region.(4)In the sample added with Y2O3,the dispersion phase particles remain high density and evenly dispersed in the crystal grains after hot rolling,and the average size of the dispersed phase particles in FeCrWY-ODS steel is 4.1nm and 6.3nm(Ti added)respectively;The average size of dispersed phase in FeCrWAl-ODS steel is 6.5nm and 9.5nm(Ti added),the smaller dispersed phase particle is Y2O3,and the larger(about50nm)particle is Y4Al2O9 with monoclinic structure.In samples added with Ti,Ti and C combine to form carbides.(5)The hot rolled samples show higher room temperature tensile strength and high temperature strength:ODS steel added with Y2O3 shows excellent high temperature strength,of which FeCrWY-ODS steel has a maximum tensile strength of 320MPa at700?and FeCrWAl-ODS steel has a maximum tensile strength of 250MPa at 700?.The high temperature tensile strength of FeCrWAl series samples is obviously improved after hot rolling. |
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