Preparation Of FeCrAl Cladding Materials And Effects Of Cr On The Properties

In recent years,with the shortage of traditional energy,the importance of nuclear power is increasing.With the occurrence of a series of nuclear facilities accidents,people gradually realize that the second and third generation nuclear power systems,which are widely used at present,cannot meet the safety requirements.Many countries are seeking to develop the fourth-generation nuclear power system.As the first barrier of nuclear safety protection,the performance of fuel cladding tube is the most important issue.In the process of serious nuclear accident of Fukushima nuclear power plant in 2011,the Zr alloy cladding material used at present was oxidized rapidly under accident conditions,resulting in core damage and hydrogen explosion.Therefore,Zr alloy has been unable to meet the performance requirements of the fourth-generation nuclear power system for cladding materials.FeCrAl ferritic alloy has been paid more and more attention because of its good performance in the field of thermal power generation,and it has rapidly become one of the candidate materials for cladding of the fourth-generation nuclear power system.In this paper,the phase composition and thermodynamic properties of Fe-x Cr-6Al alloy were predicted by JMat Pro software,and the composition range and rolling process of Fe-x Cr-6Al alloy were designed.The rolling process of 400??1200?and the recrystallization annealing process of 700??1100?was designed and applied on the Fe-13Cr-6Al alloy in order to study the influence of hot rolling and recrystallization annealing on the grain size and the deformation recrystallization mechanism of Fe-x Cr-6Al alloy.Then the mechanical properties,thermophysical properties and high temperature water vapor corrosion resistance of the Fe-x Cr-6Al alloy were studied.At last,the deformation mechanism of FeCrAl alloy was revealed by molecular dynamics calculation,and the effect mechanism of Cr element on the thermophysical properties of FeCrAl alloy was further explored.The research found the following rules:(1)The change of grain size of Fe-13Cr-6Al alloy rolled at 400??1200?and recrystallized at 700??1100?shows that the larger the deformation storage energy is,the lower the recrystallization temperature and the smaller the recrystallized grain are.Defined by the rolling force and grain size of Fe-13Cr-6Al after hot roll and recrystallization annealing,the optimized rolling process was rolling at 800?and recrystallization annealing at 1000?,at which the grain size is 421?m.(2)SEM and XRD analysis on samples of FeCrAl with different content of Cr reveal that when the content of Cr increased from 11 wt%to 15 wt%while Al remains constant,the phase structure of Fe-x Cr-6Al does not change.The lattice constant of Fe-x Cr-6Al alloy increased by up to 5.2%.The mechanical properties of the Fe-x Cr-6Al alloy are improved and the density is reduced by up to 1.9%,the hardness of the Fe-x Cr-6Al alloy is increased by 9.7%,and the compressive yield strength is increased from 370 MPa to 394 MPa.The weight gain of Fe-x Cr-6Al alloy within 1200?high temperature water vapor environments was first increased from0.158 mg/cm~2 to 0.586 mg/cm~2 and then decreased to 0.293 mg/cm~2.The thermal capacity and the coefficient of thermal expansion was little influenced by the variation of Cr content.(3)The molecular dynamics model of FeCrAl alloy was established,and the effects of Cr and Al on the phase stability,thermal properties and mechanical properties of the alloy were analyzed.It was found that Cr is favorable for the stability of ferrite phase,while Al is unfavorable for the stability of ferrite phase.Cr content has little effect on the lattice constant and thermal expansion coefficient of the alloy,but with the increase of Al content,the lattice constant of the alloy increases,the thermal expansion coefficient decreases,and the change of specific heat capacity of the alloy can be ignored.At 300 K,with the increase of Cr content,the bulk modulus and Poisson's ratio increased and the shear modulus decreased,with the Al content remains constant;with the increase of Al content,the bulk modulus first increased and then decreased,the shear modulus decreased and the Poisson's ratio increased,with the Cr content remains constant.