Study On The Preparation Technology Of Y-Ti-O Dispersion Strengthened CLAM Steel

Energy crisis is one of the main problems restricting the economic development of all countries in the world.Nuclear power because of its reliable,green,efficient,clean,etc.,is expected to replace fossil fuels,attracting more and more attentions.At present our country is in the vigorous development of the nuclear power industry.ODS(oxide dispersion strengthened)steel due to distribution of fine oxide particles,has excellent high temperature performance and anti-irradiation properties,and was expected to become the future fusion reactor structural materials of the first wall structural materials.CLAM(China' low activation martensitic)steel is under China's independent research for the International Thermonuclear Experimental Reactor(ITER).Similar to other RAFM(Reduced activation ferritic-martensitic)steels,the service temperture of CLAM steel is 250?550?.In this paper,by adding Ti and Y2O3 pre-milled powers to the basis of CLAM powder,to develop ODS-CLAM steel,with more excellent high temperature performance steel by mechanical alloying method.Different from the traditional preparation technology of ODS steel,this paper adopts a two-step milling method.The first step is to make pre-milled Ti-Y2O3 alloy powder,to make Ti and Y elements completely solid solution.Second step,CLAM steel power with good atomization was put in to secondary mechanical ball milling,completing the ODS steel powder preparation.Through the package,pumping and other preparatory work,the ODS steel was prepared under the conditions of 1150?/150MPa/4h for hot isostatic pressing(HIP).The microstructure and mechanical properties of ODS steel were studied.By means of scanning electron microscope,laser particle size analyzer,X-ray diffraction and thermal analyzer,the research on effects of different milling time,alloy composition and other parameters on the properties of alloy powder,were carried out to determine the best milling process:using a planetary mill,fixed speed 450r/min,ball milling time for 70h,ball to powder ratio 8:1,atmosphere of argon.Hydrogen reduction experiments were carried out to study the effect of hydrogen reduction on the oxygen in the powder of ODS steel.The microstructure and basic mechanical properties of ODS steel after heat treatment were studied.In the matrix of ODS steel,there were a large number of small particles with the size of 5?10nm.And the grain size is not uniform,ranging from tens of nanometers to several microns.Chemical mapping analysis showed that it is rich in Y,Ti,0 elements.Tensile test at room temperature shows that tensile strength of ODS steel is about 1265MPa,and yield strength is 1065MPa,which are about double that of CLAM steel.But the toughness is obviously decreased.The optimization of the preparation process of ODS steel has also been discussed.