Dynamic Recrystallization Modeling and Mechanisms in Inconel 690 Alloy during Hot Compressive Deformation
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JMEPEG https://doi.org/10.1007/s11665-020-05213-x
Dynamic Recrystallization Modeling and Mechanisms in Inconel 690 Alloy during Hot Compressive Deformation D.S. Li
, X.Y. Shang, W. Wang, E.X. Zhao, G. Chen, and P. Gao
Submitted: 27 February 2020 / Revised: 4 September 2020 / Accepted: 19 September 2020 The dynamic recrystallization (DRX) behavior of INCONEL 690 (IN690) alloy was studied using electron backscatter diffraction (EBSD) and transmission electron microscopy. Isothermal compression tests were performed on a Gleeble-3500 simulator under temperatures 950-1100 °C, strain rates 0.01-1 s21, and the maximum true strain 0.8. An Avrami-type model was developed to investigate the DRX behavior of IN690; it was found to be extremely sensitive to the processing parameters of temperature, strain rate, and true strain. As temperature increased and strain rate decreased, the activation energy increased, thus accelerating movement of dislocation and migration of grain boundaries, causing DRX behavior acceleration. The DRX behavior is accompanied by dislocation rearrangement and annihilation. The DRX mechanism of IN690 is dominated by discontinuous dynamic recrystallization (DDRX) and supplemented by continuous dynamic recrystallization (CDRX). A key characteristic of DDRX is grain-boundary bulges, while CDRX features progressive sub-grain rotation, leading to migration of low-angle grain boundaries to high-angle grain boundaries. A series of constitutive models were embedded into finite-element method software to study the DRX behavior of IN690. The results show that the microstructure evolution regularity obtained by the simulation method is consistent with the experimental values, which provides a basis for computer simulations of the hot machining process. Keywords
dynamic recrystallization, hot compression, IN690 alloy, nucleation mechanism, numerical model
1. Introduction INCONEL 690 (IN690) alloy is a nickel-based superalloy, which is considered a substitute for IN600 due to its lower carbon content and higher nitrogen content (Ref 1). IN690 alloy has been widely used in nuclear power plant steam-generator heat pipes due to its excellent mechanical performance, good formability, and high resistance to stress corrosion cracking (Ref 2). However, hot extrusion is a key step during IN690 pipeline manufacturing, which may cause pipeline cracks due to work hardening (WH) (Ref 3, 4). Thus, thermal deformation is used as a method to optimize the microstructure and improve the mechanical properties of IN690 alloy. The dynamic recrystallization (DRX) behavior of IN690 alloy is extremely sensitive to processing parameters, including temperature, strain rate, and true strain. Some complex metallurgical phenomena need to be addressed during hot processing, including WH, dynamic recovery (DRV), and DRX (Ref 5). Therefore, it is vital to study the microstructural evolution of IN690. The Johnson–Mehl–Avrami equation is commonly utilized to explore the DRX behaviors of different materials and has
D.S. Li, X.Y. Shang, W. Wang,
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