Delta Phase Characterization in Inconel 718 Alloys Through X-ray Diffraction

Nunes, Rafael Menezes; Pereira, Daniel; Clarke, Thomas Gabriel Rosauro; Hirsch, Thomas

doi:10.2355/isijinternational.isijint-2015-111

Cited by 37 publications

(7 citation statements)

References 7 publications

(9 reference statements)

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“…Consistent with the DSC analyses, no trace of γ′ and γ″ were detected at the FESEM after aging at 870 °C, with the rapid formation and growth of the δ plates occurring both at the grain boundaries and inside the grains. The intragranular δ plates were oriented in a regular pattern relative to each other based on a parallelepiped grid due to the well-known crystallographic relationship between the δ phase and the γ matrix [51,90,91]: (010)δ∥{111}γ,[100]δ∥false〈1true1¯0false〉γ.…”

Section: Discussionmentioning

confidence: 99%

Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting

et al. 2019

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Nickel-based Inconel 718 is a very good candidate for selective laser melting (SLM). During the SLM process, Inconel 718 develops a complex and heterogeneous microstructure. A deep understanding of the microstructural features of the as-built SLM material is essential for the design of a proper post-process heat treatment. In this study, the microstructure of as-built SLM Inconel 718 was investigated at different length scales using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Electron backscatter diffraction (EBSD) was also used to analyze the grain morphology and crystallographic texture. Grains elongated in the build direction and crossing several deposited layers were observed. The grains are not constrained by the laser tracks or by the melt pools, which indicates epitaxial growth controls the solidification. Each grain is composed of fine columnar dendrites that develop along one of their <100> axes oriented in the direction of the local thermal gradient. Consequently, prominent <100> crystallographic texture was observed and the dendrites tend to grow to the build direction or with occasional change of 90° at the edge of the melt pools. At the dendrite length scale, the microsegregation of the alloying elements, interdendritic precipitates, and dislocations was also detected.

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Section: Discussionmentioning

confidence: 99%

Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting

et al. 2019

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“…As reported in the literature [13], large numbers of δ phase precipitated in the alloy are detrimental for sample mechanical properties because it competes Nb elements with γ” phase. Meanwhile, appropriate amounts of δ at grain boundaries can restrain the grain growth, which is beneficial for enhancing the mechanical properties [11,12]. For the 950AC+aging samples, the content of δ phases was large (see Figure 4) and their sizes were larger than those in the 1000AC+aging samples.…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, when solution-treated at 1000 °C, more alloying elements could diffuse into the matrix lattice, which is thermo-dynamically favorable for precipitating γ”/γ’ phases. In the 1080AC+aging samples, no needle-shaped δ phase could be found because 1080 °C exceeds the solvus of δ phase (around 1050 °C [11]). Consequently, grain growth could not be restricted by the grain boundary δ phases.…”

Section: Discussionmentioning

confidence: 99%

“…The γ” phase is metastable and can transform into the δ (Ni 3 Nb) phase at high temperatures [7,8,9]. Appropriate amounts of δ phases at grain boundaries can refine the grain sizes and improve the resistance to grain boundary creep fracture [10,11,12]. However, large amounts of δ phases will decrease the mechanical strength, since it consumes Nb atoms, leading to the loss of γ” phases in this alloy [13].…”

Section: Introductionmentioning

confidence: 99%

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Enhancing Mechanical Properties of the Spark Plasma Sintered Inconel 718 Alloy by Controlling the Nano-Scale Precipitations

Yan

Wang

et al. 2019

Materials

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The present study aimed to optimize the phase constituents and mechanical properties of the spark plasma sintered (SPS) Inconel 718 (IN718) alloy. A series of heat treatment routes were designed based on the phase relations in IN718 and performed for the optimization. The microstructure and phase compositions of the SPS IN718 alloys were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), and transmission electron microscopy (TEM). The mechanical properties of the samples were characterized at room temperature and at 650 °C. The results showed that large amounts of γ” (Ni3Nb) and γ’ (Ni3(Al, Ti)) strengthening phases precipitated in the IN718 alloy after direct aging (DA) of the as-fabricated sample. Moreover, the mechanical properties of the DA sample were comparable to that of the best one of the solution-treated and aged counterparts. The analysis showed that the rapid sintering and solid solution treatment of the IN718 alloy were achieved simultaneously by SPS. In the case of the SPS IN718 material, the direct aging regime had the same heat treatment effect as the conventional solid solution and aging treatment. This contributes toward improving the production efficiency and reduces manufacturing costs in the actual production process.

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“…δ phase in certain quantities and morphologies can lead to a loss in fracture toughness [25][26][27]. Although the precipitation range for the δ phase is between about 700 and 1000 °C [28][29][30], the δ phase precipitation does not occur in the modified solid solution specimen after aging for 4 h at 750 °C, as shown in Fig. 5b.…”

Section: Aging Treatment Processesmentioning

confidence: 94%

Optimization of Microstructure and Mechanical Properties of Hipped Inconel 718 by Various Heat Treatment Processes

El-Bagoury

Hessien

Alsawat

et al. 2019

Metallogr. Microstruct. Anal.

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The influence of heat treatment processes on hardening and harmful phases in microstructure and mechanical properties of hipped Inconel 718 (IN718) alloy was investigated. In comparison with conventional solid solution treatment, modified solid solution one entirely eradicates δ phase from the microstructure of hipped IN718 alloy. However, a thin film of δ phase precipitates at the grain boundaries of γ matrix. Aging at 750 °C for 4 h, another morphology of needle-like δ phase appeared as small colonies in the microstructure of IN718 alloy. Prolonging the aging duration time to 50 h, these colonies enlarge in size and spread in the whole matrix. X-ray diffraction and transmission electron microscope observations were used to identify different phases such as γ, γ′, γ″, and δ in the microstructure of IN718. Hardness property was measured representing the mechanical properties of investigated heat-treated IN718 alloy. Conventional solutionized specimens have higher rate in hardness increasing with aging time compared to modified solutionized ones. The latter specimens need an incubation period of about 24 h to ascent suddenly achieving the same hardness level of the other corresponding specimens. These heat treatment conditions are considered as the best compromise to achieve the optimum mechanical properties.

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Delta Phase Characterization in Inconel 718 Alloys Through X-ray Diffraction

Cited by 37 publications

References 7 publications

Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting

Texture and Microstructural Features at Different Length Scales in Inconel 718 Produced by Selective Laser Melting

Enhancing Mechanical Properties of the Spark Plasma Sintered Inconel 718 Alloy by Controlling the Nano-Scale Precipitations

Optimization of Microstructure and Mechanical Properties of Hipped Inconel 718 by Various Heat Treatment Processes

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