Uniaxial Tensile Deformation Behavior And Constitutive Modeling Of 22MnB5 Boron Steel For Automobile Body

Automotive lightweight has become an effective measure to reduce fuel consumption,reduce carbon emissions and achieve China's carbon-neutral goal by 2050.In order to realize automotive lightweight,high-strength steel is more and more used in automotive body manufacturing.As a typical representative of high strength steel,22MnB5 boron steel has become one of the most commonly used materials for critical structures in impact.In order to explore the deformation mechanism of 22MnB5 boron steel and improve the application of 22MnB5 boron steel in the body structure,it is necessary to fully study the deformation behavior,microstructure and constitutive model of 22MnB5 boron steel at different temperatures.The 22MnB5 boron steel sheet was used in the present work.Through uniaxial tensile experiments at different temperatures,the thermal deformation behavior of 22MnB5 boron steel under quasi-static load and different temperature is analyzed.The voce constitutive model with Johnson cook model strain rate term and Arrhenius constitutive model with Zener-Hollomom factor with strain term are constructed respectively.In addition,the effect of heat treatment on deformation behavior of 22MnB5 boron steel was discussed based on microstructure.The following conclusions were drawn.(1)As the heat treatment temperature increases,the fraction of lath martensite of the studied steel increases,and the yield strength and tensile strength also increase significantly.In addition,as the increase of strain rate,the yield strength and tensile strength of the studied steel first increase and then decrease.(2)Based on the original Voce constitutive model,a modified model was built by introducing the strain rate term of the Johnson-Cook constitutive model.The constitutive fitting results are basically with the experimental results with R of 0.993 and AARE of 3.15%,indicating that the modified constitutive model can character the mechanical behavior of the studied 22MnB5 steel.(3)When the deformation temperature is 500? 650? and 700?,and the strain rate is 0.01 s^-1,the undercooled austenite of the experimental steel transforms,resulting in the second rapid increase of flow stress,especially when the deformation temperature is 500?.At other temperatures and strain rates,the steady flow stress decreases with the increase of deformation temperature.(4)Based on the original Arrhenius constitutive model,the Zener-Hollomom factor containing the strain term was used to fit the experimental data,and the parameters to be determined were fitted by polynomial.The obtained constitutive equation can better describe the rheological mechanical variation trend of 22MnB5 boron steel.(5)The parameters of energy dissipation efficiency are closely related to the deformation behavior of 22MnB5 boron steel during hot deformation,and different deformation temperatures,strain rates and strains have great effects on the energy dissipation efficiency value.Based on the dynamic material model and Prasad instability zone criterion,the thermal processing diagram of 22MnB5 boron steel was constructed.The optimal thermal processing process of 22MnB5 boron steel was determined as deformation temperature of 850?950? and strain rate of 0.01?0.1 s^-1.