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Journal ArticleDOI

Precipitation of the δ-Ni 3 Nb phase in two nickel base superalloys

TL;DR: In this article, the precipitation of the metastable δ-Ni3Nb phase has been studied in two niobium bearing nickel base superalloys and the morphology and distribution of precipitates have been examined and the crystallographic orientation relationship between the austenite and the δ phases has been determined.
Abstract: The precipitation of the equilibrium δ-Ni3Nb phase has been studied in two niobium bearing nickel base superalloys—INCONEL 718 and INCONEL* 625—both of which are hardenable by the precipitation of the metastableγ″-Ni3Nb phase. The morphology and the distribution of precipitates have been examined and the crystallographic orientation relationship between the austenite and theδ phases has been determined. The nucleation of theδ phase at stacking faults within pre-existing δ" precipitates has been discussed.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a combination of ∆ g parallelism rule, good matching site (GMS) analysis, CSL/DSCL (coincidence site lattice/displacement shift complete lattice) and the O-lattice theory has been applied to interpret the observation of the habit plane (HP) of the δ precipitates and the linear defects in the HP in an Inconel 718 superalloy.
Abstract: A calculation method based on a combination of ∆ g parallelism rule, good matching site (GMS) analysis, CSL/DSCL (coincidence site lattice/displacement shift complete lattice) and the O-lattice theory has been applied to interpret the observation of the habit plane (HP) of the δ precipitates and the linear defects in the HP in an Inconel 718 superalloy. The small scattering in the HP orientation around an ideal rational plane is interpreted by the existence of a mixture of two types of steps with different heights and inclinations. These steps play a significant role to enhance the degree of matching in the HP. They are associated with secondary dislocations, with Burgers vectors of \(1/6\left[ {1\;1\;\bar{2}} \right]_{\gamma } / 1/3[0\;0\;1]_{\delta }\), and with a direction parallel to a near-invariant line along \([1\;\bar{1}\;0]_{\gamma }\). The spacing of the secondary dislocations projected on the terrace plane is around 6.3 nm. The calculated dislocation structure is in good agreement with the observation.

4 citations

Journal ArticleDOI
01 Feb 2021
TL;DR: In this paper, the research and application of nickel base superalloy GH4169 in recent years was introduced, which has been widely used in aeroengine, petroleum, nuclear industry and other fields The phase composition, three common heat treatments as well as the application prospect were elaborated
Abstract: In this paper, the research and application of nickel base superalloy GH4169 in recent years was introduced GH4169 alloy is a precipitation strengthened nickel base superalloy, which has been widely used in aeroengine, petroleum, nuclear industry and other fields The phase composition, three common heat treatments as well as the application prospect were elaborated At last, the service temperature range and application area of GH4169 alloy was believed to be further expanded with the adjusted alloy composition and the corresponding hot working process

4 citations


Cites background from "Precipitation of the δ-Ni 3 Nb phas..."

  • ...δ-Ni3Nb phase is a stable phase with DOa ordered orthorhombic structure, which is not coherent with the γ matrix [10]....

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Journal ArticleDOI
TL;DR: In this article, the design and use of combinatorial samples produced on a commercial laser powder bed fusion system to study 60 distinct process conditions of nickel superalloy 625 was demonstrated.

4 citations

Dissertation
24 Sep 2019
TL;DR: In this article, the hydrogen embrittlement of Ni-base corrosion resistant alloys (CRAs) can occur when components under stress are exposed to hydrogen in deep sea oil wells.
Abstract: Hydrogen embrittlement of Ni-base corrosion resistant alloys (CRAs) can occur when components under stress are exposed to hydrogen in deep sea oil wells. Ni-base CRAs, such as alloy 718, are primarily strengthened by precipitation of γ” and γ’, and the effect of these precipitates on hydrogen embrittlement is not well understood. To better understand hydrogen embrittlement of γ” and γ’ strengthened Ni base CRAs, the hydrogen embrittlement susceptibilities and fracture modes of alloy 718 microstructures with variations in the γ” and γ’ precipitates and without grain boundary δ phase were evaluated through incremental step load (ISL) and rising displacement (RD) testing of circular notch tensile (CNT) specimens coupled with the direct current potential drop (DCPD) technique and with in situ cathodic hydrogen charging. Ki, the stress intensity factor for crack initiation, was generally independent of microstructure. Crack growth resistance and Ku, the stress intensity factor for the onset of unstable crack growth, were highly dependent on variations in the γ” and γ’ precipitates. At a constant strength level, the transition from under aged to over aged γ” decreased crack growth resistance and Ku. Increasing size of under aged γ” decreased hydrogen embrittlement susceptibility, in terms of increasing crack growth resistance and Ku, despite increasing the strength level. These results demonstrate that high strength conditions with high hydrogen embrittlement resistance can be produced. Crack initiation appeared as fine faceted transgranular cracks on {111} planes and occurred at the transition from Stage I to Stage II of strain hardening when the slip band spacing is surmised to reach a minimum value. The requirements for crack initiation are localization of deformation to the nucleated slip bands and a high concentration of hydrogen. Crack growth was dominated by transgranular cleavage on {100} planes with visible river marks, cracking on Σ3 twin boundaries, and cracking on general grain boundaries and was caused by dislocations piled up at Lomer-Cottrell locks and grain boundaries in combination with hydrogen absorbed directly at the crack tip. The γ” and γ’ precipitates alter the strain hardening behavior which changes the crack tip stresses and strains required to propagate the crack and thereby influences crack growth resistance. There was no evidence of trapping at the γ” and γ’ precipitates from thermal desorption spectroscopy (TDS) experiments of specimens pre charged with gaseous deuterium. The hydrogen embrittlement response of a microstructure with an intermediate strength level that contained δ phase was also evaluated. Transgranular crack initiation on {111} planes was observed for the δ containing microstructure at a similar Ki to microstructures without δ phase indicating that δ phase does not affect this fracture mode. Grain boundary δ phase caused unstable intergranular crack propagation at a low applied stress. The ISL test coupled with the DCPD technique allowed for identification of crack initiation…

4 citations

Journal ArticleDOI
TL;DR: In this paper, the precipitation kinetic and behavior of δ phase in Inconel 718 alloy at 900, 930 and 960°C have been studied using the quantitative X-ray diffraction (XRD) method.
Abstract: The precipitation kinetic and behavior of δ phase in Inconel 718 alloy at 900, 930 and 960°C have been studied using the quantitative X-ray diffraction (XRD) method The results indicated that the nucleation site and way of δ phase depended on temperature by the observation of microstructures During the aging process, the δ phase nucleated on the grain boundaries and twin boundaries preferentially, while the δ phase precipitated directly from the interior of grain when the temperature was above 900°C At a certain aging temperature, the relationship between the δ phase content and the aging time fitted an Avrami-type equation

4 citations

References
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Book
01 Jan 1958
TL;DR: The Handbook of Lattice spacings and structures of metals and alloys as discussed by the authors is a handbook of argumentative essay structure spacing and lattice plane model modified by the incorporation of thermodynamic functions appropriate to the f.c.
Abstract: For the best product experience, a Handbook of of argumentative essay structure spacing Lattice Spacings and Structures of Metals and Alloys ScienceDirect. Get this from a library! A handbook of lattice spacings and structures of metals and alloys. (W B Pearson) Acm metal). Vol. lattice plane model modified by the incorporation of thermodynamic functions appropriate to the f.c.c. Al—Ag solid zones in the alloys. W. B. Pearson, Handbook of Lattice Spacings. Structures of Metals and Alloys.

3,090 citations

Book
01 Jan 1962
TL;DR: Modern Physical Metallurgy as mentioned in this paper describes the fundamental principles of physical metallurgy and the basic techniques for assessing microstructure and provides a balanced coverage of properties, characterization, phase transformations, crystal structure, and corrosion not available in other texts.
Abstract: Modern Physical Metallurgy describes, in a very readable form, the fundamental principles of physical metallurgy and the basic techniques for assessing microstructure This book enables you to understand the properties and applications of metals and alloys at a deeper level than that provided in an introductory materials course The eighth edition of this classic text has been updated to provide a balanced coverage of properties, characterization, phase transformations, crystal structure, and corrosion not available in other texts, and includes updated illustrations along with extensive new real-world examples and homework problems It offers renowned coverage of metals and alloys from one of the world's leading metallurgy educators It covers new materials characterization techniques, including scanning tunneling microscopy (STM), atomic force microscopy (AFM), and nanoindentation It provides the most thorough coverage of characterization, mechanical properties, surface engineering and corrosion of any textbook in its field It includes new worked examples with real-world applications, case studies, extensive homework exercises, and a full online solutions manual and image bank

421 citations

Book ChapterDOI
TL;DR: In this article, a review of theoretical models applicable to concentrated solid solutions is presented, focusing on concentrated solutions because dilute ones can be considered as special cases and because the interesting effects of clustering and ordering are most apparent at high solute concentrations.
Abstract: Publisher Summary This chapter reviews current theoretical models applicable to concentrated solid solutions. It focuses on concentrated solutions because dilute ones can be considered as special cases and because the interesting effects of clustering and ordering are most apparent at high solute concentrations. The extended ranges of solubility are often found in metallic systems, and for this reason most examples selected will refer to metals and alloys, although the models presented are equally applied to off-stoichiometric compounds, metallic or inorganic, and to amorphous solids. The chapter provides description of the state of the order of the system through suitable averaging procedures. It discusses the internal energy of solutions, from both electronic and elastic standpoints. The chapter presents free energy models, such as generalized Bragg- Williams's model, Landau theory, and cluster variation method. These models are applied to the study of phase equilibrium.

308 citations

Journal ArticleDOI
TL;DR: In this article, a heat treatment for 706 alloy was developed which effectively optimizes the 1200°F stress-rupture properties of the alloy by precipitation of globular to plate-like Ni3Cb/Ni3Ti at the grain boundaries in conjunction with maintaining a fine as-forged grain structure.
Abstract: Evaluation of a commercial heat treatment for 706 alloy indicated that it resulted in relatively low 1200° F stress rupture ductility. It was determined that this was caused by a solution treatment which dissolved all of the age-hardening phases in the alloy and caused a coarse grain size and supersaturated matrix condition. Based upon extensive fine structure study of the 706 alloy as well as previous experience with 718 alloy and other Fe−Ni-base superalloys, a heat treatment is developed which effectively optimizes the 1200°F stress-rupture properties of the alloy. The key to best properties was found to be the precipitation of globular to plate-like Ni3Cb/Ni3Ti at the grain boundaries in conjunction with maintaining a fine as-forged grain structure.

44 citations