Hot Deformation Behavior And Solution And Aging Process Of Fe-Mn-Al-C Low Density Steel

Automobile exhaust is an essential source of pollutants in the urban atmospheric environment.It is imperative to reduce automobile exhaust emissions.Automobile lightweight can effectively reduce exhaust emissions and effectively reduce vehicle energy consumption,in line with the requirements of the national"two-carbon"strategy.Iron and steel material is a vital body materials with excellent strength,but their high density limits the development of automobile lightweight.Fe-Mn-Al-C series low-density steel has good mechanical properties,and its density is usually below 7g/cm3,which can effectively reduce the weight of the automobile and is a significant development direction of automobile steel in the future.However,there are still many problems in the regulation of the strength and toughness of low-density steel,which limit the improvement of mechanical properties.Therefore,through the combination of experimental research and numerical simulation,this paper studies the hot deformation behavior and solution aging process system of Fe-Mn-Al-C low-density steel,explores the reasonable hot working system of low-density steel,and provides theoretical guidance for effectively improving the mechanical properties of low density steel.The main research content of this paper is as follows:（1）The thermal deformation behavior of Fe-Mn-Al-C low-density steel was studied through the thermal compression experiment and the microstructure analysis.The thermal deformation constitutive equation of low density steel was established,and the hot working diagram of low density steel was drawn.The rational hot working process system was obtained by analyzing the unstable zone and safe zone of different strain hot working diagrams.The results show that the stress of low-density steel increases with the increase of strain rate and decreases with the growth of deformation temperature.The rational thermal working parameters are deformation temperature 1000℃-1150℃and strain rate0.01s^-1-0.5s^-1.（2）Based on the hot compression data,a dynamic recrystallization dynamic model of low density steel was established,and the DEFORM finite element software was used to simulate the hot deformation process of low density steel.The simulation results were in good agreement with the experimental results,which verified the accuracy of the simulation results.The results show that the dynamic recrystallization volume fraction increases with the increase of strain variable and deformation temperature,and decreases with the increase of strain rate.The dynamic recrystallization volume fraction of low-density steel core under the same deformation condition is the highest.（3）The effects of different solution and aging processes on the microstructure and mechanical properties of low-density steel were studied.The results show that with the increase of solution temperature and solution time,the grain size of the low-density steel grows gradually,the carbide dissolves into the matrix slowly,the strength of the steel decreases gradually,and the plasticity increases first and then decreases.The reasonable solution process is 950℃+1h;After aging treatment,the carbide precipitates in the grain,and the grain has no noticeable change.Too high an aging temperature and too long an aging time will precipitate the carbide along the grain boundary.With the increase in aging temperature and aging time,the strength of low-density steel gradually increases,and the plasticity gradually decreases.The reasonable aging process is 500℃+4h.