Study On Hot Deformation Behavior And Deformation Mechanism Of A100 Steel

A100 steel has been widely used in aircraft landing gear due to its excellent strength plasticity synergy,fracture toughness,stress corrosion cracking resistance and fatigue performance.Forging and machining are usually used in its manufacturing process to implement the“control shape and performance”of parts.Therefore,the research on the hot deformation behavior and deformation mechanism of A100 steel under different process parameters plays a pivotal role in guiding the microstructure and performance control during the forging process.In this paper,the Arrhenius phenomenological constitutive model and physical constitutive model based on deformation parameters were constructed and the hot deformation behavior of A100 steel was analyzed.The hot processing map under Prasad and Murty flow instability criteria was established and the steady-state deformation and flow instability zones were predicted.The dynamic recrystallization mechanism of A100 steel was discussed by using dynamic recrystallization kinetic model combined with microstructure characterization results.The main research results are as follows:（1）Hot compression tests were performed on A100 steel in the deformation temperature range of 800°C～1200°C,and the strain rate range of 0.01s^-1～10s^-1.At the true strain of 0.6,the flow stress increases rapidly and reaches the peak value and then tends to steady state.The flow stress decreases with the increase of temperature and the decrease of strain rate.Arrhenius phenomenological constitutive model and constitutive model based on physical parameters were established respectively,and the flow stress of A100 steel under different hot deformation conditions was predicted.The results show that the average correlation coefficient is 0.9675 and0.9649,and the average relative error is 4.7877%and 4.3679%,respectively.The BP artificial neural network model was introduced into the research on the hot deformation behavior of A100steel,and a three-layer network model was established.Based on the stress-strain curve of hot compression test and a suitable step size,the prediction of flow stress value of A100 steel under different hot deformation conditions is realized after the self-learning and training process of the model.Using the theory of hot processing map,based on the flow instability criterion of Prasad and Murty,a hot processing map is constructed.The instability area for the flow instability region of the hot deformation process of A100 steel is concentrated in the low temperature and high strain rate zone.The region suitable for processing is mainly located in the high temperature and low strain rate zone.（3）The critical strain model and kinetic model for dynamic recrystallization of A100 steel are established.It is found that the critical strain for initiation of dynamic recrystallization increases when the strain rate increases or the temperature decreases.As the strain rate decreases or the temperature increases,the dynamic recrystallization volume percentage increases.Combined with the microstructure characterization,the dynamic recrystallization mechanism of A100 steel is discussed.The mechanism of dynamic recrystallization of A100 steel at lower temperature is the grain boundary bowing mechanism,while at the higher temperature is the subgrain merger mechanism.