Study On Thermal Deformation Behavior And Deformation Mechanism Of Low Density Steel With Ni And Si

In recent years,low-density steel has become an inevitable trend for auto motive lightweight steel due to its many advantages in resource conservation and environmental protection.Currently developed high-manganese high-aluminu m low-density steel has high strength,high ductility,etc.Structural components have great potential for application.However,there are still some problems to be solved in the application of high-manganese high-alumina steel to industrial production,especially the edge cracking problem that occurs during hot rolling.This paper focuses on the thermal processing behavior and microstructure evolu-tion of Mn26Al9Ni3Si steel,analyzes the deformation mechanism of Mn26Al9Ni3Si steel,establishes the mathematical model of deformation resistance,and uses three different thermal processing maps based on the dynamic material mo del to predict the hot rolling process.The possible hot rolling defects provide a theoretical basis for the formulation of hot-working processes in the actual pr oduction process.There are six chapters in this thesis.The main experimental work and con clusions are as follows:(1)The single-pass compression related experimental data were extractedand the high-temperature deformation behavior of Mn26Al9Ni3Si steel was stud ied.By comparing and analyzing the fitting accuracy of the selected mathemati cal model,the deformation resistance model of Mn26Al9Ni3Si steel with a fitti ng accuracy of 0.938 was obtained.(2)The dynamic recrystallization of Mn26Al9Ni3Si steel was studied by combining the microstructure after single-pass compression.The results show that Mn26Al9Ni3Si steel easily undergoes dynamic recrystallization when lnZ is not more than 33.51.The results of metallographic structure and theoretical calculations show that dynamic recrystallization is more likely to occur when Mn26Al9Ni3Si steel undergoes plastic deformation under low temperature and high strain rate.(3)TEM microscopic characterization of the deformed microstructure under isothermal constant strain rate,the deformation mechanism of Mn26Al9Ni3Si steel was studied.The results show that Mn26Al9Ni3Si steel has twins at 850~oC,and no deformation twins are observed in the microstructure after the temp erature rises to 1050 ~o C.That is,the high temperature is not conducive to the formation of twinning of Mn26Al9Ni3Si steel.(4)The thermal processing map of Mn26Al9Ni3Si steel is drawn based on three different destabilization criteria.The microscopic defects that may occur in the steel are predicted.It is determined that the Murty criterion is more suit able for the development of the optimum thermal processing parameters of Mn26Al9Ni3Si steel.Experiments have verified that the grain size of the processe d material within the process range is fine and uniform.