Research On The Structure And Mechanical Properties Of Fe-28Mn-10Al-0.8C Low-density High-strength Steel

With the global energy crisis and increasingly serious environmental problems,the automotive industry is moving along the lightweight model.And as a new type of Fe-Mn-Al-C low-density high-strength steel,in ensuring its excellent comprehensive mechanical properties at the same time,its low density,good corrosion resistance is looked at the future direction of development of automotive steel.In this paper,the microstructure and performance of Fe-28Mn-10Al-0.8C low-density and high-strength steel was studied by means of composition design,smelting process,hot compression deformation,forging forming,solution treatment and room temperature tensile deformation.Design components in Fe-28Mn-10Al-0.8-C series single-phase austenitic low density of the material.The Gleeble-3500 thermal simulation test machine was used to study the high temperature compression test of the experimental steel at the selected deformation temperature(850～1100 ℃)and strain rate(0.01～10s-1).We can find that The flow stress-strain curves of single-phase austenitic Fe-28Mn-10Al-0.8C steel show typical dynamic recrystallization.The peak stress of the experimental steel increases with the decrease of the deformation temperature and the increase of the strain rate under isothermal compression.The dynamic recrystallization behavior of experimental steels is very sensitive to deformation temperature and strain rate.Increasing the deformation temperature or reducing the strain rate will promote the dynamic recrystallization and grain growth of austenite.The nucleation rate and the growth rate of the dynamic recrystallized grains of Fe-28Mn-10Al-0.8C steel increase with the increase of the deformation temperature.With the increase of the strain rate,the nucleation rate of the dynamic recrystallization increases and the grain size decreases,and the microstructure of the final austenite dynamic recrystallization grains is smaller.The mechanical properties and the evolution of the microstructures under the conditions of different solid solution treatment were studied.It was found that the microstructure of the forged test steel and the room temperature under different reaction conditions was a single austenite phase and no phase change occurred.And in the austenite matrix distribution of a large number of deformation twins and annealing twin,twins throughout the austenite grain.With the increase of the solid solution temperature of the experimental steel and the prolonging of the holding time,the austenite grains are coarsened and the recrystallized grains grow up obviously.There is a large amount of white second phase precipitation in the room temperature structure under experimental steel forging conditions.The energy spectrum analysis shows that it is containing Nb,Ti and other carbides.And a large number of slip bands appear in the austenite grains.With the increase of the solid solution temperature of the experimental steel and the prolonging of the holding time,the slip zone gradually disappears and the white precipitated phase gradually dissolves in the austenite matrix.And finally in the fast cold water quenching conditions less than precipitation and retained in the matrix to improve the comprehensive mechanical properties of materials.With the increase of the solution temperature and the prolonging of the holding time,the elongation and strong plasticity of the test steel are gradually increased,and then gradually decreases.The strength and hardness of the test steel are gradually reduced with the increase of the solution temperature and the holding time.It was found that the elongation at break and the strong plasticity were the highest when the solution temperature was 1050℃for 1h,and the comprehensive mechanical properties of the material were the best.