Microstructural modeling and simulation for GCr15 steel during elevated temperature deformation

doi:10.1016/j.matdes.2013.10.042

Materials & Design

Volume 55, March 2014, Pages 560-573

https://doi.org/10.1016/j.matdes.2013.10.042 Get rights and content

Highlights

•
Formulated the constitutive model for microstructural evolution of GCr15 steel.
•
Observed the optical micrograph of GCr15 steel after hot deformation process.
•
Confirmed the accuracy and reliability of the developed constitutive models.
•
Simulated the microstructural evolution of GCr15 steel during hot deformation.

Abstract

The microstructural evolution of GCr15 steel, one of the most commonly used bearing steels, was investigated and simulated by physical experiments and finite element method (FEM). Physical experiments were conducted on the Gleeble-3500 thermo-simulation system. Effects of initial grain size and plastic strain on the microstructural of the materials were investigated by setting different heating temperature, holding time and deformation degree, respectively. Based on the results of stress–strain curves and metallographic analysis, the constitutive equations for flow stress, austenite grain growth and dynamic recrystallization of GCr15 steel were formulated by linear regression method and genetic algorithm. In addition, the coupled thermo-mechanical finite element method integrated with the developed constitutive models was used to simulate the microstructural evolution of GCr15 steel during hot compression. Good agreement between the calculated and experimental results was obtained, which confirmed that the developed constitutive models can be successfully used to predict microstructural evolution during hot deformation process for GCr15 steel.

Introduction

Extensive investigations over the past few decades have shown that several heat-activated metallurgical phenomena, such as grain growth, dynamic recovery, dynamic recrystallization and phase transformation, will occur during hot deformation process [1], [2]. Those metallurgical phenomena will greatly affect the microstructure of the processing materials and play an important role in determining the mechanical performance of the products [3], [4], [5]. To guarantee and improve the mechanical performance of the products, the microstructure of materials during hot deformation process should be carefully and precisely controlled.

With the development of numerical simulation method, finite element method provides us an effective tool to simulate and predict the microstructural evolution of materials during hot deformation process [6], [7], [8], [9]. During the establishment of the FE simulation model, one of the vital things is to formulate the constitutive relationship between the microstructural change of materials and processing parameters. In the past few decades, the microstructural change of material was always described as the function of external variables including deformation temperature, strain rate and strain history, and internal variables consisting of initial structure and material properties [10], [11]. And the empirical model presented by Sellars and Whiteman [12] have been widely used in microstructural modeling for steels during hot deformation process nowadays.

In 2012, Chen et al. investigated the dynamic recrystallization behavior of 42CrMo steel by hot compression test and proposed the kinetic equations for the dynamic recrystallization behavior of 42CrMo. Good agreement between the experimental and predicted results indicated that the proposed microstructural evolution model can give an accurate estimate of the dynamic recrystallization behavior in hot deformed 42CrMo steel [13]. Lv et al. investigated the dynamic recrystallization behavior of Mg–2.0Zn–0.3Zr alloy by hot compression experiments on Gleeble-1500 thermo-mechanical simulator as well [14]. Li et al. studied the flow behavior of Al–Zn–Mg–Sc–Zr alloy and its microstructural evolution during hot compression deformation by thermal simulation tests. Based on the experimental results, they pointed out that at higher deformation temperature or lower strain rate, the grain size as well as the volume fraction of the recrystallized grains increased [15]. Deng et al. studied the microstructure evolution of 7050 aluminum alloy by hot compression test. They concluded that the peak stress decreased with the increase of deformation temperature or the decrease of strain rate and the main softening mechanism of homogenized 7050 aluminum alloy is dynamic recovery [16]. Li et al. studied the hot deformation behavior of Ag-containing 2519 aluminum alloy by isothermal compression test and investigated the microstructural evolution of the material during deformation [17]. Ebrahimi et al. studied the dynamic recrystallization behavior of austenite in a superaustenitic stainless steel using hot compression test and investigated the effect of deformation temperature and strain rate on the flow stress during dynamic recrystallization by using the hyperbolic sine equation [18].

All the researches cited above successfully predicted the microstructural evolution of specified material during hot deformation process via physical experiments or FE simulation method. As one of the most commonly used bearing steels, GCr15 steel (AISI-52100) has the characteristics of high wear resistance, corrosion resistance and good dimensional stability. It has been widely used in manufacturing bearing ring, ball screw and other mechanical components via hot deformation techniques [19]. To guarantee and improve the mechanical performance of the products, microstructural evolution of GCr15 steel during hot deformation process should be carefully and precisely controlled. However, literatures aiming at microstructural modeling and simulation for GCr15 steel during elevated temperature deformation have never been reported according to the authors’ knowledge.

In this study, the microstructural evolution of GCr15 steel during hot deformation process was investigated and simulated by physical experiments and finite element method (FEM). To formulate the constitutive equation for austenite grain growth of GCr15 steel, specimen with diameter of 8 mm and height of 12 mm was heated to the temperature range of 950–1150 °C with holding time range of 0–480 s on the Gleeble-3500 thermo-simulation system. Isothermal compression experiments were carried out in the temperature range of 950–1150 °C and in the strain-rate range of 0.1–10 s⁻¹ to study the dynamic recrystallization phenomenon for GCr15 steel. Based on the experimental results and metallographic analysis, the constitutive equations for flow stress, austenite grain growth and dynamic recrystallization of GCr15 steel were revealed by linear regression method and genetic algorithm subsequently. In addition, a finite element simulation model integrated with the developed constitutive models was successfully established on the DEFORM-2D platform to simulate the microstructural evolution of GCr15 steel during hot deformation process. Research results indicated that the calculated results agree well with the experimental results, which confirmed that the developed constitutive models can be successfully used to predict microstructural evolution for GCr15 steel during hot deformation process.

Section snippets

Materials and experimental procedure

The material used in this study is the GCr15 continuous casting slab. Table 1 shows the chemical composition of the material. Specimens with diameter of 8 mm and height of 12 mm were manufactured from the center of the slab. To formulate the constitutive equations for austenite grain growth and dynamic recrystallization for GCr15 steel, isothermal heating and compression experiments were conducted on the Gleeble-3500 thermo-simulation system, respectively.

Fig. 1(a) illustrates the experimental

Austenite grain growth

Fig. 3 illustrates the optical micrographs of prior austenite grain boundaries of GCr15 steel with heating temperate of 950 °C followed by different subsequent isothermal holding time. It can be seen from Fig. 3 that the average austenite grain size increases with the increment of the subsequent isothermal holding time. The average austenite grain size of heated GCr15 steel with holding time of 0 s, 120 s, 300 s and 480 s is 11.157 μm, 19.380 μm, 23.560 μm and 25.120 μm, respectively.

Fig. 4 illustrates

Conclusions

In this investigation, the constitutive models for microstructural evolution of GCr15 steel during hot compression process was successfully investigated and revealed by physical experiments and finite element simulation method. The entire macro–micro constitutive models can be seen as follows:

(a)
Flow stress $\dot{ε} = 3.326 e 12 {[\sinh (0.00824 σ)]}^{4.80311} \exp (- 306005 / RT)$
(b)
Austenite grain growth model $d^{4.133} = d_{0}^{4.133} + 6.685 \times 10^{31} t \exp (- 6.8 \times 10^{5} / RT)$
(c)
Dynamic recrystallization model $ε_{c} = 0.78 ε_{p}$

ε_{p} = 0.0338 d_{0}^{0.0342} {\dot{ε}}^{0.1968} \exp (23550 /

Acknowledgements

This work was supported by the State Key Development Program for Basic Research of China (Grant No. 2011CB706605), the General Program of National Natural Science Foundation of China (No. 50975215), the National Natural Science Foundation for Young Scientists of China (No. 51005171) and “the Fundamental Research Funds for the Central Universities (No. 125107002)”. The authors would like to gratefully acknowledge the support from them.

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Microstructural modeling and simulation for GCr15 steel during elevated temperature deformation

Highlights

Abstract

Introduction

Section snippets

Materials and experimental procedure

Austenite grain growth

Conclusions

Acknowledgements

Mater Sci Eng A

Mater Sci Eng, A

J Mater Process Technol

Mater Des

J Mater Process Technol

Comp Mater Sci

Mater Des

Mater Sci Eng, A

Mater Sci Eng A

Mater Sci Eng A

Mater Sci Eng A