The Properties Of Ordered Phase In Fe-Mn-Al-C Low Density High Strength Steel And Its Effect On Mechanical Properties Of Steel

Low density and high strength steel has good properties such as low density,corrosion resistance,and high strength and toughness.The steel has great potential in the fields of automobile,military industry,chemical industry,and so on.At the same time,it has broad prospects in the application of automotive lightweight and safety.The ordered phase in low density and high strength steel is mainly B2?Fe,Mn?Al and DO₃?Fe,Mn?3Al.However,the content of these ordered phases in low density and high strength steel is less,and under certain conditions will be generated.At present,there is less research of ordered phase,so in this paper,we calculated the stability,the electronic structure,mechanical properties and Debye temperature of Fe-Al intermetallic compound and Fe-Mn-Al alloy by the theoretical calculation and experimental method.And also we study the microstructure and mechanical propertiesof Fe-Al compounds.At the same time,we further study the microstructure and mechanics properties of Fe-Mn-Al-C steel.These study can provide theoretical basis and data support for low density high strength plastic special steel new material industrialization.The main results are as follows:The cohesive energy and formation enthalpy is negative of this Fe-Al compounds,DO₃ type Fe-Mn-Al alloy and B2 Fe-Mn-Al alloy,indicating that they are thermodynamic stability.These alloys have structural stability by the mechanical stability conditions.We calculated the bulk modulus,shear modulus,hardness and Young's modulus and Poisson's ratio of these compounds.Research shows the DO₃ Fe-Mn-Al alloy have good plasticity and low strength,B2 type Fe-Mn-Al alloy have poor plasticity and high strength.At the same time,we investigated the mechanical anisotropy of these compounds,which indicates that these compounds have a strong anisotropy of Young's modulus.Through study the electronic structure and the Debye temperature of these compounds,we can found that these compounds are mainil combination by covalent bond and metallic.Meanwhile,also exist anti-bond effect.We also synthesized Fe3Al and FeAl compounds by experiment,and we studied the microstructure and mechanical properties,show that FeAl alloy has high hardness and strength,but has poor plasticity;Fe3Al alloy has low strength and hardness,but has good plasticity.Finally,we also studied the microstructure and mechanical properties Fe-Mn-Al-C steel,show that the experimental steel is dual phase steel,the austenite and ferrite are matrix.By XRD phase analysis,we found that the B2 and DO₃ ordered phase exist in organization.Even after high temperature solution treatment,the B2 and DO₃ ordered phase can still exist.With the increase of solution temperature,the content of ordered phase in the steel is getting lower and lower.By studied the tensile strength at room temperature,we found that the tensile strength decrease with the solution temperature increasing,while the elongation increases with the solution temperature increasing.Therefore,we speculate that the ordered phase can improve the strength and reduce the ductility of steel.