Research On Hot Deformation Behavior Of 904L Super Austenitic Stainless Steel And Dynamic Recrystallization Simulation

904L super austenitic stainless steel is widely used in energy,chemical industry and other fields because of its excellent corrosion resistance.Especially,in the process of production,hot rolling process plays an important role in the final performance and surface quality of products.During hot rolling,physical metallurgical behaviors such as grain deformation,dislocation movement and dynamic recrystallization occur in the material.Because of its high alloy content,it is easy to appear mixed grains,deformation twins,adiabatic shear band and other adverse phenomena during deformation,which affect the product quality and mechanical properties.In addition,the establishment of a reasonable prediction model of thermal deformation and dynamic recrystallization behavior is the basis for the prediction of microstructure and properties in industrial production.Therefore,the single pass hot compression experiment of 904L super austenitic stainless steel was carried out at 900～1150℃ and strain rate of 0.01～10 s-1,and the hot deformation behavior and dynamic recrystallization behavior of the material were studied.Based on DEFORM-3D software,the microstructure evolution of the material during hot compression was simulated.The main conclusions are as follows:(1)Under the experimental conditions,the flow stress of the material decreases with the increase of deformation temperature and the decrease of strain rate;Considering the bulging phenomenon of the compression specimen,the flow stress curve is modified by introducing the friction coefficient;the modified peak stress and the flow stress constitutive model considering the strain compensation are established,and the model values are in good agreement with the experimental values,the average error is less than 10%.(2)Based on the theory of dynamic material model,the processing map with different strain variables is obtained.It indicates when the strain is high(ε=0.7),the maximum value of power dissipation efficiency appears at 1070～1150℃,0.3～2 s-1,which is the suitable range of thermal deformation parameters for the steel in this experiment.By means of the microstructure characterization and microhardness,the correctness of the processing map is verified by image method.At the same time,it is found that the more dynamic recrystallization degree is,the higher the microhardness is,that is,the microhardness increases with the increase of deformation temperature and strain.(3)The critical strain model and volume fraction model of dynamic recrystallization of materials are established.The dynamic recrystallization grain size model is established by statistical analysis of dynamic recrystallization grains.The results show that with the increase of temperature and the decrease of strain rate,the dynamic recrystallization grain size dDRX and volume fraction XDRX increase.For dynamic recrystallization critical strain εc,the value decreases when the temperature increases and the strain rate decreases.(4)The dynamic recrystallization model is embedded in DEFORM-3D software to simulate the thermal compression and microstructure evolution of materials.The results show that the dynamic recrystallization volume fraction and grain size obtained by simulation are in good agreement with the experimental values.In addition,the optimum range of thermal deformation parameters obtained in the heat treatment drawing is verified.