Study On Microstructures And Mechanical Properties Of Medium Manganese Lightweight Steels With Superior Strength And Ductility

In recent decades,China's economy and society have developed rapidly.While the number of cars is increasing,oil shortages and environmental pollution problems have become more prominent.The effective way to solve these problems is to achieve lightweight vehicles.Fe-Mn-Al-C low-density steels have attracted much attention due to their excellent mechanical properties.The research history of Fe-Mn-Al-C lightweight steel is short,and many mechanisms are still unclear.Most of the research has been focused on high manganese steels,but there are not many studies on medium manganese lightweight steels.Therefore,this paper takes medium manganese steel as the research object,and analyzes the microstructures and mechanical properties of the experimental steel under different annealing temperatures,providing a basis for practical applications.In this paper,Fe-12Mn-7Al-0.6C and Fe-12Mn-7Al-0.6C-0.5V experimental steels were designed.Through mechanical property testing and microstructure analysis,the influencse of annealing temperatures and microalloying element V on the microstructures and mechanical propertie and the evolution mechanism of dislocations under different deformation conditions are investigated.The results obtained from the experiments are summarized as follows:1.The effect of annealing temperature on the microstructure and mechanical properties of medium manganese high aluminum low density steel was obtained.In the annealing treatment range between 800 and 1100?,as the annealing temperature increases,the austenite and ferrite grain size increases,the strength decreases,and the elongation increases first and then decreases.2.When annealled at 900?,the strength of Fe-12Mn-7Al-0.6C steel reaches 820MPa and the ductility is 23%.A certain amount of V element is microalloyed in the medium manganese high aluminum steel to form fine VC precipitates.Due to the refinement of the microstructure,the strength and ductility of the material have been improved.When the V-containing steel is annealed at 900?,the tensile strength is 860 MPa and the elongation is 29%.3.The results of microstructure observation show that the planar slip occurs in austenite,and the spacing of the slip bands decreases with the deformation processing.The wavy glide occurs in ferrite,forming dislocation tangles and dislocation cellular structure..The addition of V reduces the slip band spacing in austenite and increases the dislocation density in ferrite.