Thermal deformation behavior and constitutive equation of ultra-high strength 25MnB steel for automobile
The uniaxial isothermal compression tests of 25MnB steel were carried out on the MMS-200 thermal simulator,and the true stress-true strain curves of 25MnB steel were obtained at 850-1150 ℃,with the maximum true strain of 0.7,and the can strain rates of 0.01,1,10 and 30 s-1,respectively.The results show that the main softening mechanism of the material is dynamic recrystallization with low strain rate,and the deformation mechanism of the material with high strain rate is work hardening-dynamic recovery.A modified Ar-rhenius-type constitutive equation was established by introducing the Zener-Hollomon parameter and using the stress-strain data.The ther-mal deformation activation energy of 25MnB steel under the peak stress state is 297.376 kJ·mol-1.Based on the peak stress constitutive equation,the effect of strain on the material constant is included in the constitutive analysis.By comparing the experimental data and pre-dicted data,the applicability of the established constitutive equation was evaluated using the correlation coefficient and the average abso-lute relative error.The results show that the constitutive equation considering strain compensation has a good prediction for the flow stress of 25MnB steel.
25MnB steelhigh temperature flow behaviorconstitutive equationstrain compensation
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