Unified Modelling of Flow Stress and Microstructural Evolution of 300M Steel under Isothermal Tension

Rongchuang Chen,Shiyang Zhang,Min Wang,Fei Feng,Xianlong Liu

doi:10.3390/met11071086

Rongchuang Chen, Shiyang Zhang + Show 3 more

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https://doi.org/10.3390/met11071086

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Abstract

Constitutive models that reflect the microstructure evolution is of great significance to accurately predict the forming process of forging. Through thermal tension of 300M steel under various temperatures (950~1150 °C) and strain rates (0.01~10 s−1), the material flow and microstructure evolutions were investigated. In order to describe both the exponential hardening phenomenon at a higher temperature, and the softening phenomenon due to recrystallization at a lower temperature, a constitutive model considering microstructure evolution was proposed based on the Kocks–Mecking model. It was found that considering the stress-strain curve to be exponential in the work-hardening stage could improve the constitutive model prediction precision. The average error was 2.43% (3.59 MPa), showing that the proposed model was more precise than the modified Arrhenius model and the Kocks–Mecking model. The models to describe recrystallization kinetics and average grain size were also constructed. This work enabled the Kocks–Mecking model to predict stress-strain curves with a higher accuracy, and broadened the applicable range of the Kocks–Mecking model.

Highlights

The constitutive model is of great significance for the accurate prediction of the forming process of forgings
The flow behavior of steel is influenced by the process parameters, and at the microscopic level the flow behavior is closely related to the evolution of the microstructure
The results showed that the evolution of flow stresses was mainly influenced by the mobile and forest dislocation motion

Summary

Introduction

The constitutive model is of great significance for the accurate prediction of the forming process of forgings. The flow behavior of steel is influenced by the process parameters (temperature, strain rate, strain, and holding time, etc.), and at the microscopic level the flow behavior is closely related to the evolution of the microstructure. The development of an accurate constitutive model reflecting the evolution of the microstructure is important to improve the forming accuracy and serviceability of forging. Various phenomenological constitutive models have been proposed, such as the Johnson–Cook (JC) model, Arrhenius model, Zerilli–Armstrong (ZA) model, artificial neural network (ANN) models and their modifications. Li et al [1] used the JC model for the development of hot compression for Cr8Mo2SiV tool steel. Ahmadi et al [2]

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