Modeling Dynamic Recrystallization Kinetics in BS 080M46 Medium Carbon Steel: Experimental Verification and Finite Element Simulation

Utilized the experimental data to construct models that describe DRX kinetics and the evolution of grain size, employing the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation, this study investigates the dynamic recrystallization (DRX) characteristics and the microstructure evolution within BS 080M46 medium carbon steel under high-temperature conditions. Several trials were carried out to analyze hot compression, covering a temperature range of 900°C to 1200°C and utilizing varying strain rates of 0.1, 1, and 10 s-1. The incorporation of these models into QForm V10.2.1 facilitated finite element modeling (FEM) simulation, enabling the evaluation of DRX behavior. A comparative analysis was carried out to confirm the efficacy of the developed models, aligning the simulation results with the data obtained through metallographic observations. The high level of agreement between the simulation and experimental findings related to the DRX grain size was quantified by a correlation coefficient (R) of 0.991, along with an average absolute relative error (AARE) of 7.412%. These results confirm the capability of the developed DRX kinetics and grain size evolution models in accurately predicting the grain size of BS 080M46 medium carbon steel.  In addition, the study suggests that higher temperatures or lower strain rates can result in an increased volume fraction of dynamic recrystallization (DRX) and grain size. This highlights the importance of Finite Element Method (FEM) as a crucial tool for comprehending the evolution of microstructure during hot working processes.

BS 080M46 medium carbon steel; DRX behavior; Finite element modeling; Grain size; Hot compression test

BS 080M46 is a versatile medium carbon steel known for its excellent mechanical properties and ease of processing, making it ideal for high-stress applications requiring wear resistance. Its strength, toughness, and wear resistance have led to its widespread use in various machinery parts such as gears, axles, crankshafts, and connecting rods, as well as in shafts, bolts, studs, and hydraulic cylinders (Mizuguchi et al., 2009). Typically, during the hot working process of BS 080M46 medium carbon steel, the material is heated to a temperature exceeding the recrystallization temperature range. This allows for the material to be plastically shaped and formed easily using various hot working processes, including hot forging, hot rolling, and hot extrusion (Altan, 2005). Lv et al. (2018) emphasized that thermo-mechanical processing, utilized in the production of large structural components, tailors the microstructure for desired mechanical properties, necessitating predictive models due to the sensitivity of the microstructure to processing conditions, and the intricate relationship between processing parameters, material deformation behavior, and resulting microstructures.

In the realm of metallurgy, three significant phenomena – work hardening (WH), dynamic recovery (DRV), and dynamic recrystallization (DRX) – significantly shape the flow behavior, microstructure, and energy required during the hot working process, occurring concurrently during material deformation and controlling flow stress under varying conditions (Derazkola et al., 2022; Kooiker, Perdahcioglu, and Boogaard, 2018). These phenomena ultimately impact material properties and behavior, playing a critical role in determining the quality of the final product (Chen et al., 2021b). Through these occurrences, the microstructure evolution of metals is notably influenced by DRX. The existing coarse grains undergo notable deformation and eventually transform into smaller, equiaxed grains, contributing to both grain refinement and homogenization (Bharath et al., 2021; Zheng et al., 2018; Quan, 2013). Consequently, this process leads to enhanced mechanical properties, particularly in terms of increased strength, ductility, and toughness (Tukiat et al., 2024; Zou et al., 2022; Anwar et al., 2021; Kurnia and Sofyan, 2017; Kozmel et al., 2014). The effects of DRX on metals depend on several factors, including the composition of the metal, the deformation temperature, the strain rate, and the processing history (Alaneme and Okotete, 2019). In addition, the occurrence of DRX and the resulting microstructure can also be affected by prior cold work, which may require higher processing temperatures or longer processing times to achieve DRX (Stefani et al., 2016; Sanrutsadakorn, Uthaisangsuk, and Suranuntchai, 2014).

Precisely characterizing the DRX behaviors and the mechanisms of grain evolution is of utmost importance for achieving the desired microstructure and mechanical properties. The construction of DRX kinetic models has involved several attempts to represent material behavior and the evolution of grain size effectively. Studies by Hu and Wang (2020) and Yang et al. (2018) have shown that flow curves can represent the hot working behaviors of BT25y titanium alloy and 5CrNiMoV steel, respectively, due to their close correlation with microstructural changes. Therefore, stress-strain data derived from isothermal compressions can be employed to formulate DRX kinetics, with the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation widely utilized to depict the correlation between the volume fraction of deformation-induced DRX, deformation temperature, and strain rate (Irani et al., 2019). For instance, Wang et al. (2016), through their research, established an Arrhenius-type constitutive equation incorporating a Zener-Hollomon parameter, along with DRX volume fraction and grain size models, all based on the JMAK equation. This comprehensive approach accurately describes the deformation behavior observed during the hot-working processes of the carburizing steel alloy 20Cr2Ni4A. Similarly, models for the DRX volume fraction and grain size, applicable to 33Cr23Ni8Mn3N heat-resistant steel, were developed by Ji et al. (2020) and integrated these models into the DEFORM-3D software. The finding stemming from microstructural observations obtained through LOM and SEM, along with finite element simulations, exhibited highly consistent, thereby validating the precision of the established DRX model. Quan et al. (2019) investigated the DRX behavior of AlCu4SiMg alloys using the JMAK equation and verified its feasibility through both FE simulations and experiments. Additionally, studies on various alloys such as Ti-5Al-5Mo-5V-3Cr-1Zr near b Titanium alloy (Lv et al., 2018), medium Mn steel (Sun et al., 2020), solution-treated Ni-based superalloy (Chen et al., 2016), Cr8 alloy (Chen et al., 2022), and TB8 Titanium alloys (Zhang et al., 2020) used FEM simulations of DRX behavior. The concordance between simulation results and microstructural observations underscores the potential of finite element simulations as valuable tools for predicting the DRX behavior across various alloys, which can be helpful in designing and optimizing manufacturing processes for these materials.

        Despite extensive research into understanding dynamic recrystallization (DRX) phenomena in various alloys, the specific behavior of DRX in BS 080M46 medium carbon steel remains relatively unexplored. This knowledge gap presents significant challenges in optimizing the hot working processes of this material to achieve the desired microstructural characteristics and mechanical properties. Furthermore, the lack of accurate predictive models tailored to BS 080M46 medium carbon steel further hinders process optimization efforts. Therefore, the present work aims to address these challenges by studying the DRX behavior and microstructure evolution of BS 080M46 medium carbon steel through hot compression testing. Experimental data were collected to establish both a DRX kinetics model and a grain size model based on the JMAK equation. These models were subsequently incorporated into QForm V10.2.1 software to simulate microstructure evolution, with a specific emphasis on grain size under different deformation conditions. By comparing these finite element simulation results with microstructure observations, the accuracy and reliability of the models are verified. Providing insights into DRX behavior specific to BS 080M46 medium carbon steel and developing accurate predictive models, this study aims to contribute to the advancement of metallurgical science and materials engineering, facilitating enhanced process optimization and product development in engineering applications.

        The material being studied is BS 080M46 medium carbon steel, which was supplied by S.B.-CERA Co., Ltd. The weight percentage (wt%) of the steel's chemical composition was analyzed using an Emission Spectrometer (OES) and is detailed in Table 1. Figure 1(a) illustrates the conceptual methodology diagram used in this study. The flow curves under high temperatures required for input into the finite element model were obtained by a hot compression test using a Baehr DIL-805 deformation dilatometer. Samples were prepared in a cylindrical shape, 5 mm in diameter and 10 mm in height, with a thermocouple attached to the surface for direct temperature detection during deformation. The hot compression test covered four temperatures: 900°C, 1000°C, 1100°C, and 1200°C, along with three strain rates: 0.1, 1, and 10 s^-1, to characterize deformation conditions. Samples were placed in a vacuum chamber filled with inert Argon gas and heated by an induction coil to reach the deformation temperatures. The heating rate of 1.625°C/s was maintained for 1 minute to ensure uniform temperature distribution. Samples were then compressed using an Alumina punch to achieve a 60% reduction in height, followed by immediate quenching in Argon gas with a cooling rate of 40°C/s until reaching room temperature. Figure 1(b) depicts the temperature–time path during the hot compression test. Metallographic preparation involved cutting samples along the cylindrical axis, mounting them on a hot press, initial polishing with 400-grit SiC abrasive paper, followed by finer grits up to 1200 grit SiC papers and 0.3 µm Alumina particles for final polishing. Subsequently, surfaces were etched using a 4% picral and 3% Nital solution for 4 seconds. Microstructural observations were conducted using Light Optical Microscopy (LOM) and scanning electron microscopy (SEM), focusing on the central region of the sample’s cross-sections. The initial microstructure of BS 080M46 medium carbon steel contains proeutectoid ferrite and pearlite, as depicted in Figure 2.

Table 1 Chemical compositions (wt%) of BS 080M46 medium carbon steel