First-principles Study On Materials Properties And Corrosion Of Fe-Cr-Si Alloy

Ferritic martensitic steels show excellent geometric stability and corrosion resistance under intense irradiation environment.Ferritic martensitic steels include lots of Fe and Cr elements and a little Si,C,N and so on.FeCr alloy is one of the important candidate materials for nuclear reactor.Meanwhile,the FeCr alloy is one of the important stainless steel materials.The FeCr alloy can be applied to various fields,such as the nuclear power plant and infrastructure.Usually,the FeCr alloys show disordered lattice structure,complex magnetism and so on.The experiments are still the primary methods to study the properties of the alloy.Therefore,the study of FeCr alloy is limited due to the influence of temperature,pressure and so on.It is an important task for researchers employing appropriately theoretical methods to study the physical properties and pitting corrosion of the alloy.In this work,the research contents are divided into two sections,including study of bcc Fe-Cr-Si binary and ternary random alloys from special quasi-random structure and studying on pitting corrosion of Al deoxidation stainless steel with rare earth element(La)treatment.The main research contents are as follows:Firstly,we use a combination of first-principles calculations with special quasi-random structure and quasi-harmonic approximation methods.We calculate the relation between formation energy,magnetic moments,mechanical properties and thermodynamic properties of binary FeCr random alloys and Cr concentration.Subsequently,we dope the Si element into FeCr alloys and keep the constant Cr concentration to generate the FeCr Si ternary alloys.Then,we study the effect of Si on formation energy,antiferromagnetic interaction,magnetic moments,mechanical properties and thermodynamic properties of the alloys.In the second section,the first-principles calculation is employed to study the pitting corrosion of Al deoxidation stainless steel with rare earth element(La)treatment.We compare the calculation results using GGA-PBE and LDA functions to experimental phenomena.The results indicate that PBE function is suitable for subsequent calculations.We discuss the corrosion mechanism and corrosion propagation direction depended on Mn S,Cr₂O₃and Al₂O₃ inclusions.We also study the relation between corrosion and electrical conductivity of inclusions.And then we study the effects of microcrevices on local corrosion depended on Al₂O₃.We conclude that the new inclusions with La element are generated by the formation energy of reaction equations.Meanwhile,we calculate the resistance to corrosion of inclusions with La element.The inclusion cluster Al₂O₃-Mn S is also an important object of study in this work.The corrosion of inclusion cluster is discussed according to the corrosion stages and propagation direction.We also pay attention to Cu concentration in the alloy and the effect of Cu on local corrosion in the La treatment process.The calculational results of Fe-Cr-Si alloys material properties and corrosion are agree with experimental results.It is helpful for assisting researchers to implement more relevant work.The study shows certain theoretical and practical significance.