Flow behaviour and constitutive modeling for hot deformation of austenitic stainless steel

Abstract

The flow behavior of 316H austenitic stainless steel is investigated using hot compression tests. The modified Johnson-Cook and Zerilli-Armstrong models are developed, and modified Arrhenius-type model is established using an approach by dividing low and high stress region for determining key material constant and an uncomplicated approach for compensating strain in which the activation energy is determined from peak stress and only other material constants are considered as strain-dependent constants. The performance of all developed constitutive models is comparatively analyzed. It is indicated that the significant sensitivity of flow stress to temperature and strain rate is exhibited, and at 900 and 950 °C, strain rate sensitivity is closely related to temperature and strain rate, which can be explained by low stacking fault energy for 316H austenitic stainless steel. The modified Arrhenius type model has a noticeably higher accuracy in predicting flow behaviour than other two developed models in spite of a good performance of all developed models according to visual examination and statistical analyses.

Constitutive Descriptions and Restoration Mechanisms of a Fe-17Cr Alloy during Deformation at Temperatures of 700–1000 °C

“…This can be explained in term of the stacking fault energy. A similar sensitivity of the effect of strain rate on flow stress to deformation temperature has been observed and proved in other stainless steels [28,36].…”

“…The JC model describing the flow behavior of metals can be expressed as follows [ 39 ]: where the means of σ , ε , , , T , T r , T m , A 2 , n 1 , A 3 , n 2 and A 1 are identical to those reported in Reference [ 28 ]. Clearly, a coupled effect of temperature and strain rate on the flow stress, which is observed in Section 3.1 , is not considered in this model.…”

“…Subsequently, the parameters for other reference temperatures and strain rates are determined. By using these parameters, the predicted flow stresses can be acquired and eventually be employed for determining the different average absolute relative errors ( AARE s) under different reference conditions ( Supplementary Materials Figure S1h ) which can be expressed as follows: where M , P and N are identical to those reported in Reference [ 28 ]. At 850 °C and 1 s −1 , the minimum AARE of 3.4% is obtained.…”

“…The Arrhenius-type model describing the flow behavior of metals can be expressed as follows [ 42 ]: where the means of A , n , A ′, n ′, A ″ and β , α , Q and R are identical to those reported in Reference [ 28 ]. In addition, the Zener-Holloman parameter Z describing the effects of temperature and strain rate on flow stress is shown by using the equation below [ 40 ]: …”

“…For the Johnson-Cook (JC) models, an important problem that needs to be addressed is that, generally, the material parameters B 5 , λ 1 and λ 2 (as stated in Equation (2) in this study) are all considered to be constants. As a matter of fact, according to studies about the establishment of JC model [16,[28][29][30][31][32], these material parameters obtained by linear fitting are markedly different at different strains and are related to strains. This is to say, the conventional approach could introduce some errors into the parameters, which will decrease the reliability and stability of the developed constitutive model.…”