Materials Design Of Automotive Steel With High Strength Combined With High Elastic Modulus

Atomobile lightweight is of great significance for energy saving,emission reduction and environmental protection.There are two ways to achieve lightweight,which are material lightweight and structure lightweight.Material lightweight can be achieved by adding lightweight elements to reduce material density.Structure Lightweight can be achieved by reducing the thickness of automobile components.However,the stiffness decreases when the material thickness decreases.Since the stiffness is only related to the elastic modulus and thickness of the material,therefore,in order to reduce the thickness of materials and meet the stiffness requirements,only the elastic modulus of materials can be improved.Existing studies have shown that adding TiB2 particles is an effective way to improve the elastic modulus of materials.At present,the third generation of advanced high-strength steel is widely used because of high strength,and this paper is devoted to the research of the development of advanced high-strength steel with high elastic modulus.high strength and low density.In this paper,the mechanical properties were measured by WDW-50KN electronic testing machine.The heat treatment experiment was completed by SGL-1400-11 tubular heating furnace.The austenite content was measured by XRD diffractometer.The microstructure of the experimental steel were observed and by metallographic microscope and scanning electron microscopy.The content of this paper is divided into two parts.The first part is the design of matrix structure of automotive steel with high strength combined with high elastic modulus.The second part is the research on properties of automotive steel with high strength combined with high elastic modulus Through the study of the composition-process-mircostructure-property of the experimental steel,the following conclusions are drawn as follows:(1)The matrix composition is designed as Fe-15Mn-4Al and Fe-15Mn-3Al.The innovation of the matrix design lies in the fact that it does not rely on C as a means of strengthening and toughening.(2)For Fe-15Mn-4Al experimental steel,the ferrite can not be removed after quenching at 1000℃ for 5h.After annealing at 600℃,the mechanical properties are not ideal and the austenite stability is not stable enough.(3)For Fe-15Mn-3Al experimental steel,the ferrite is completely eliminated after quenching at 900℃ for 1h,and the ideal matrix structure is obtained.After annealing at 510℃,530℃ and 550℃ for 12h and 24h,it is found that the mechanical properties are best after 530℃ for 24h.The yield strength is 310MPa,the tensile strength is 650MPa,and the elongation is 32%.After annealing,the austenite is relatively stable.Therefore,the final matrix composition is determined as Fe-15Mn-3Al,and the heat treatment process is set to 900℃+1h+water cooling+530℃+24h+air cooling.(4)The Fe-15Mn-3Al-2B-4.7Ti experimental steel has a density of 7.112g/cm3 and an elastic modulus of 21 8GPa after adding TiB2,which satisfies the requirements of light weight and high elastic modulus.After the same heat treatment process as Fe-15Mn-3Al experimental steel,the Fe-15Mn-3Al-2B-4.7Ti experimental steel has a tensile strength of 810MPa,yield strength of 720MPa and elongation of 5.6%.The strength is greatly improved,but the elongation is lower.In order to improve the elongation,it is necessary to further study the influence of TiB2 particles on the microstructure evolution,the interfacial behavior of the matrix and the fracture behavior of TiB2 particles.