Preparation And Mechanical Properties Of Rare Earth/Transition Metal Doped Castable Nanostructured Steel

Low-activated ferritic/martensitic?RAFM?steel is the most mature nuclear fusion reactor cladding structure material due to its easy mass production,good overall thermomechanical?mechanical?performance,and strong resistance against the degragation in the performance induced by neutron irradiation.The material of choice.The high-density fine precipitates and the stability of the material structure under high temperature and strong irradiation have a crucial impact on the safe service of materials.This topic is firstly based on a CNA?Castable nanostructured alloys?Fe_88.61Cr₉W_1.1Mn_0.5V_0.3Ta_0.14Si_0.25C_0.1N_0.06?wt.%?,which is then optimized by doping rare earth and transition metal elements and thermo-mechanical treatment process.The microstructure of the alloy is controlled,the influence of mechanical properties of the microstructured material is studied,.A new CNA with a high volume fraction of nano-precipitated phase,a fine grain size,high strength,high plasticity and high creep resistance is prepared.In this study,the original CNA,CNA+RE,and CNA+TM?RE:rare earth element,TM:transition metal element?alloys were prepared by smelting,casting and thermo-mechanical treatment techniques.Through the optimization of alloy composition and mechanical properties,the alloy with 0.3 wt%La elements was found to have the best comprehensive mechanical properties under the condition of rolling at 900?.Among the three types of alloys,CNA+0.3wt%La alloy after rolling has a yield strength of 1318MPa at room temperature,which is nearly 30%higher than the yield strength of original CNA alloy,1027 MPa.The uniform elongation of CNA+0.3wt%La is 6.52%,which is nealy increased by 90%when compared with that?3.25%?of original alloy CNA.After further optimizing the heat treatment process at 850?for 30 minutes,CNA+0.3 wt%La alloy was found to have the most excellent mechanical properties at room temperature.The yield strength is 1115 MPa and the elongation at failure reaches 28%.The microstructure of CNA+0.3 wt%La alloy was characterized by transimission electron microscopy.It was found that CNA+0.3 wt%La alloy with excellent mechanical properties contained a high density of nano-precipitates.The addition of La element changes the microstructure of precipitated phase and results in the formation of a unique La element cladding structure.The average grain size of the precipitated phase is about10.3 nm.Finally,the high temperature mechanical properties of CNA+0.3 wt%La alloy were studied.The tensile yield strength of CNA+0.3 wt%La alloy was about 985 MPa at500?,and 680 MPa at 600?.The CNA+0.3 wt%La alloy exhibits excellent mechanical properties at high temperatures,which will greatly improve the safe service conditions of nuclear fusion cladding materialsIn this thesis,the CNA+0.3 wt.%La alloy prepared by doped elements has a relatively high density of precipitated phase and excellent mechanical properties,which can improve the safe service conditions of the materials in the field of nuclear fusion applications,and lead to good industrial application prospects.