Evolution of the Annealing Twin Density during δ-Supersolvus Grain Growth in the Nickel-Based Superalloy Inconel™ 718

Jin, Yuan; Bernacki, Marc; Agnoli, Andrea; Bo, Lin; Rohrer, Gregory S.; Rollett, Anthony D.; Bozzolo, Nathalie

doi:10.3390/met6010005

Cited by 34 publications

(9 citation statements)

References 27 publications

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“…At the same time, a mount of annealing twin can be found 1040 °C. This is consistent with the prior findings that the amount of annealing twin increasing with the increase of grain boundaries migration rate [48].…”

Section: Effect Of Preheating Process On the Microstructure Evolutionsupporting

confidence: 93%

Microstructure Heredity of Inconel 718 Nickel-Based Superalloy during Preheating and Following Deformation

et al. 2020

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Preheating and compression tests of Inconel 718 superalloy double cone specimens were carried out to investigate the microstructure heredity during hot working. Optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were used to characterize the microstructure evolution. The results show that intense microstructure heredity can be found at the temperature 960~990 • C. During the preheating process, δ phase precipitation or grain growth could increase the fraction of high angle grain boundary (HAGBs) and Σ3 n boundaries. Otherwise, the generation or spread of annealing twin could increase the fraction of LAGBs, Volume fraction of recrystallized grains was evaluated at the whole hot working process. At the temperature of 960~990 • C, the volume fraction of recrystallized grains increases with effective strain increasing. At the super solution temperature of δ phase, the volume fraction of recrystallized grains decreases and then increases with the increase of the effective strain. The unimodal grain size distribution and fully recrystallized grains can be obtained at low strains at 960~990 • C. The twin boundary length fraction of deformed specimens is always lower than that of preheated ones. Discontinuous dynamic recrystallization (DDRX) was considered as the dominant nucleation mechanism, and continuous dynamic recrystallization (CDRX) was strengthened with the increasing grain size. Twin introduced deformation will be the main deformation mode for alloy 718 with larger grain.Crystals 2020, 10, 303 2 of 17 to the relatively low stacking fault energy of nickel-based superalloy, the recovery induced by dislocation climb and cross slip is weak [13]. Hence, recrystallization is one of the most significant mechanisms for microstructure evolution during hot working process. The recrystallization mechanism comprises the following three categories: dynamic recrystallization (DRX), meta-dynamic recrystallization (MDRX), and static recrystallization (SRX) [14]. Due to the difficulty of refining the grain size of superalloy by SRX, extensive studies have been conducted to investigate the dynamic recrystallization during hot working process [15][16][17][18][19][20][21][22][23][24][25][26][27]. It has been well accepted that the nucleation of dynamic recrystallization for superalloy includes discontinuous DRX (DDRX) and continuous DRX (CDRX) δ phase shows clearly the pinning effect on the grain growth and stimulated the nucleation of dynamic recrystallization. Otherwise, few studies have been carried out to investigate microstructure evolution right after preheating which is more consistent with actual production.The detailed investigation of microstructure evolution during TMP is usually conducted using isothermal tests based on uniaxial compression [2,[28][29][30], uniaxial tensile [31,32], torsion [33][34][35], and plane strain compression [36][37][38][39]. Workpieces are firstly annealed to ensure the initial homogeneous microstructure [...

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Section: Effect Of Preheating Process On the Microstructure Evolutionsupporting

confidence: 93%

Microstructure Heredity of Inconel 718 Nickel-Based Superalloy during Preheating and Following Deformation

et al. 2020

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“…Here the twin density is proportionally increasing with grain size from 1 h to 3 h during which the rate of recrystallization was so high. However, once recrystallization is close to completion (after 3 h of ST), the rate of twin evolution reduced tremendously, which is in agreement with literature [12,17,19]. For the samples ST for 3 to 24 h, the trend line shows a decreasing tendency of twin density as grain size increases.…”

Section: Annealing Twins In Sta Samplessupporting

confidence: 90%

“…For the samples ST for 3 to 24 h, the trend line shows a decreasing tendency of twin density as grain size increases. Two possible mechanisms are stated by Yuan and co-authors [19] to show the inverse correlation between twin density and average grain size. Smaller grains contain several twin boundaries that could be consumed by bigger grains during grain growth, that clearly reduce the number of twins.…”

Section: Annealing Twins In Sta Samplesmentioning

confidence: 95%

Studies of Post Heat Treatment of L-PBF-Inconel 718: Effects of Hold Time on Microstructure, Annealing Twins and Hardness

Tucho¹,

Hansen²

2021

Preprint

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The widely adopted temperature for solid solution heat treatment (ST) for the conventionally fabricated Inconel 718 is 1100 °C for a hold time of 1 h or less. This ST scheme is however not enough to dissolve Laves and annihilate dislocations completely in samples fabricated with Laser metal powder bed fusion (L-PBF) additive manufacturing (AM)-Inconel 718. In spite this, the highest hardness obtained after aging for ST temperatures (970 - 1250 °C) is at 1100 °C/1h [1]. The unreleased residual stresses in the retained lattice defects are potentially affecting other properties of the material. Hence, this work aims to investigate if a longer hold time of ST at 1100 °C will lead to complete recrystallization while maintaining the strength after aging or not. For this study, L-PBF-Inconel 718 samples were ST at 1100 °C at various hold times (1, 3, 6, 9, 16 or 24 h) and aged to study the effects on microstructure and hardness. In addition, a sample was directly aged to study the effects of bypassing ST. The samples (ST and aged) gain hardness by 43 – 49 %, depending on hold time. A high density of annealing twins evolved during 3 h of ST and the quantity only slightly varies for longer ST.

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“…Based on twin topologies, Bozzolo et al [62] divided the annealing twins into grain growth twins and recrystallization twins. Jin et al [63] conducted studies on the twin density evolution in case of conventional manufactured IN 718, and they maintained that the recrystallization twins are controlled by the propagation of the pre-existing twins of growing grains. As AM IN 625 is characterized by a great microstructural texture in the as-built state, the presence of growing twins is possible and it could influence the density of recrystallization twins.…”

Section: Discussionmentioning

confidence: 99%

Microstructural and Tensile Properties Anisotropy of Selective Laser Melting Manufactured IN 625

et al. 2020

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The present study was focused on the assessment of microstructural anisotropy of IN 625 manufactured by selective laser melting (SLM) and its influence on the material’s room temperature tensile properties. Microstructural anisotropy was assessed based on computational and experimental investigations. Tensile specimens were manufactured using four building orientations (along Z, X, Y-axis, and tilted at 45° in the XZ plane) and three different scanning strategies (90°, 67°, and 45°). The simulation of microstructure development in specimens built along the Z-axis, applying all three scanning strategies, showed that the as-built microstructure is strongly textured and is influenced by the scanning strategy. The 45° scanning strategy induced the highest microstructural texture from all scanning strategies used. The monotonic tensile test results highlighted that the material exhibits significant anisotropic properties, depending on both the specimen orientation and the scanning strategy. Regardless of the scanning strategy used, the lowest mechanical performances of IN 625, in terms of strength values, were recorded for specimens built in the vertical position, as compared with all the other orientations.

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Evolution of the Annealing Twin Density during δ-Supersolvus Grain Growth in the Nickel-Based Superalloy Inconel™ 718

Cited by 34 publications

References 27 publications

Microstructure Heredity of Inconel 718 Nickel-Based Superalloy during Preheating and Following Deformation

Microstructure Heredity of Inconel 718 Nickel-Based Superalloy during Preheating and Following Deformation

Studies of Post Heat Treatment of L-PBF-Inconel 718: Effects of Hold Time on Microstructure, Annealing Twins and Hardness

Microstructural and Tensile Properties Anisotropy of Selective Laser Melting Manufactured IN 625

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