Key Takeaways & Executive Findings
- •• Gradient thermal deformation induces significant microstructural inhomogeneity in GH141 superalloy, but post-dynamic recrystallization (PDRX) during delayed heat preservation effectively homogenizes the grain structure. • The dominant dynamic recrystallization (DRX) mechanism shifts from continuous (CDRX) at low temperatures to discontinuous (DDRX) at higher deformation temperatures. • PDRX is primarily governed by static recrystallization (SRX) with concurrent meta-dynamic recrystallization (MDRX), and twin-induced nucleation also contributes to recrystallization. • Controlled heat preservation after deformation is a critical processing step to achieve uniform microstructure in industrial forging of GH141 superalloy components.
Abstract
The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production. This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superalloy after gradient thermal deformation to solve the problem of microstructural inhomogeneity. Compression tests involving double cone (DC) samples were conducted at various temperatures to assess the effect of gradient strain on internal grain microstructure variation, which ranged from the rim to the center of the samples. The results demonstrate considerable microstructural inhomogeneity induced by gradient strain in the DC samples. The delay in heat preservation facilitated post-dynamic recrystallization (PDRX) and promoted extensive recrystallization in the DC samples experiencing large gradient strain, which resulted in a homogeneous grain microstructure throughout the samples. During compression at a relatively low temperature, dynamic recrystallization (DRX) was predominantly driven by continuous dynamic recrystallization (CDRX). As the deformation temperature increased, the DRX mechanism changed from CDRX-dominated to being dominated by discontinuous dynamic recrystallization (DDRX). During the delay of the heat preservation process, PDRX was dominated by a static recrystallization mechanism, along with the occurrence of meta-dynamic recrystallization (MDRX) mechanisms. In addition, the PDRX mechanism of twin-induced recrystallization nucleation was observed.
1. Introduction
In the deformation production process, the microstructure of metal materials is affected by multiple factors, including work hardening, recrystallization, and grain growth. These factors work jointly to determine the final properties of such materials. Recrystallization contributes to the microstructural evolution of metal materials after thermal deformation. Dynamic recrystallization (DRX) refers to the nucleation and growth of new grains promoted by high stored energy in metal materials during hot deformation. During the deformation of metal materials at elevated temperatures, once deformation stops, recrystallization nucleation and recrystallization grain growth at the expense of consuming stored energy continue, a microstructural evolution called post-dynamic recrystallization (PDRX) [1]. Although PDRX is not a new phenomenon, it is usually neglected, and occasionally ignoring it may lead to unreliable conclusions.
In industrial forging, slow cooling of large parts is often required, and PDRX inevitably occurs in the cooling process, which results in continuous microstructural evolution [2–5]. Sakai et al. [6] suggested that static recrystallization (SRX) and meta-dynamic recrystallization (MDRX) are the main recrystallization mechanisms of PDRX, and PDRX was affected by historical deformation and annealing parameters during the heat preservation process. Qiao et al. [7] observed that in deformed powder superalloys, multiple PDRX mechanisms appeared during the heat preservation process, including the dominant MDRX and SRX, along with the nucleation mechanisms triggered by undissolved γ' precipitates or aided by twins. Nicolaÿ et al. [2,8] revealed that for Inconel 718 alloy, MDRX was the main PDRX mechanism for microstructural evolution during heat preservation after deformation at a high strain rate of ≥0.1 s−1, and SRX was the dominant mechanism at a low strain rate of 0.001 s−1. Li et al. [9] also investigated the influences of strain rate, deformation temperature, deformation degree, and heat preservation time on the PDRX kinetics of TC18 alloy and discovered the relative sensitivity of PDRX to the strain rate. Koundinya et al. [10] observed that after a strain of 0.70, XH55 nickel-based superalloy completed PDRX after 15 s at 1050°C and obtained a completely recrystallized microstructure. Therefore, PDRX also determines the final microstructure of metal materials and contributes to the homogeneity of microstructure.
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Wenpeng Li, Panzhi Wang, Qing Wang, Jiadian Yang, Jingjing Ruan, Xin Zhou, Lilong Zhu, Liang Jiang, Hua Zhang (2025). Effect of post-dynamic recrystallization on microstructure evolution of GH141 superalloy after gradient thermal deformation. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-024-3074-6
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Frequently Asked Questions
What is the main problem addressed in this study?
The study addresses microstructural inhomogeneity in GH141 superalloy ring-rolled parts during production, which can affect mechanical properties and performance.
How does post-dynamic recrystallization (PDRX) affect the microstructure of GH141 superalloy?
PDRX during delayed heat preservation promotes extensive recrystallization, leading to a more homogeneous grain microstructure throughout the samples, especially in regions with large gradient strain.
What are the dominant recrystallization mechanisms during deformation and post-deformation heat preservation?
During deformation, DRX is dominated by continuous dynamic recrystallization (CDRX) at low temperatures and discontinuous dynamic recrystallization (DDRX) at higher temperatures. During heat preservation, PDRX is dominated by static recrystallization (SRX) with concurrent meta-dynamic recrystallization (MDRX) and twin-induced nucleation.
Why is the study of PDRX important for industrial forging?
In industrial forging, slow cooling of large parts is common, and PDRX inevitably occurs, affecting the final microstructure and properties. Understanding PDRX helps in optimizing heat treatment schedules to achieve desired microstructural uniformity.
What experimental method was used to investigate the effect of gradient strain?
Compression tests using double cone (DC) samples were conducted at various temperatures to create a gradient strain distribution from the rim to the center, allowing assessment of its effect on grain microstructure.
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