Precipitation of the δ-Ni 3 Nb phase in two nickel base superalloys
01 Mar 1988-Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science (Springer-Verlag)-Vol. 19, Iss: 3, pp 453-465
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.
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TL;DR: In this paper, the authors compared the mechanical properties of INCONEL 718 manufactured via directed energy deposition (DED) with operando thermal metrics and control and their mechanical properties were compared as a function of the time spent in the solidification and cooling temperature ranges.
15 citations
26 Apr 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the mechanical properties of Fe-20Cr-30Ni-2Nb steels with controlled microstructures were examined by conducting tensile tests and Charpy impact tests at room temperature.
Abstract: The mechanical properties of Fe–20Cr–30Ni–2Nb (at%) steels with controlled microstructures were examined by conducting tensile tests and Charpy impact tests at room temperature. The solution-treated specimen (γ-Fe single-phase) exhibited a yield strength (σy) of 210 MPa and a maximum tensile strength (σUTS) of 850 MPa. Its rupture strain (er) was more than 40%. The specimen with high area fraction of the Fe2Nb Laves phase on the grain boundaries (ρ) exhibited a higher σy of 276 MPa and adequate tensile ductility (er=29%). The specimen with high-density precipitates of the Ni3Nb phase in the grain interior exhibited a much higher σy. The value of σy of Fe–20Cr–30Ni–2Nb steel can be controlled by changing the precipitation morphology in the grain interior. Fractographic observations demonstrate that ductile intragranular fracture occurred in all of the tested specimens. The absorption energy measured by the Charpy impact test decreased from 211 to 31 J/cm2 as ρ was increased from 0% to 89%. The fracture mode appeared to vary from ductile transgranular fracture to cleavage transgranular fracture with increasing ρ. There was no indication of crack propagation within the precipitates of the Laves phase covering the grain boundaries or along the interface between γ-Fe and the Laves phase. Therefore, the Laves phase that precipitated on the grain boundaries would not have a negative effect on the room-temperature ductility.
15 citations
TL;DR: Loria et al. as mentioned in this paper examined the effects of four starting conditions on the isothermal aging response of as-forged Alloy 718 and found that the starting conditions had a significant effect on the precipitation growth kinetics of 7’ or 7”.
Abstract: The effects of four starting conditions on the isothermal aging response of as-forged Alloy 718 have been examined. As-forged Alloy 718 material was solution heat treated at either 1800F (982C) or 1950F (1066C) for 1 hour and quenched to room temperature. Samples from each solutionized condition were cold worked producing four starting conditions prior to aging. The samples from the four starting conditions were then isothermally aged at 1800F (982C), 1650F (899C), 1500F (816C), and 1200F (648C) for various lengths of time and subsequently quenched to room temperature. Microstructural analysis was performed to correlate structural changes to hardness data. The S morphology generated during isothermal aging at 1800F (982C) depends on the prior microstructure condition. The 1950F (1066C) solution condition when aged at 1800F (982C) resulted in the formation of 6 in a plate morphology . The 1800F (982C) solution condition started with platelet 6 which spheroidizes with added time. Cold working of both prior to aging at 1800F (982C) distributes the 6 more uniformly throughout the microstructure and produces a more uniform 6 size distribution. at 1650F (899C) precipitated 6, 7’) Isothermally heat treating and 7” nearly simultaneously yielding only a minor hardening response on subsequent aging. Both 7’ and 7” were observed in the 1650F (899C) and 1500F (816C aging groups. Either 7” nucleated initially or both 7” and 7’ forme d simultaneously. In this study, 7’ was never observed to form prior to 7”. Solution temperature does not appear to have a significant effect on the precipitation growth kinetics of 7’ or 7”, however, cold working promotes nucleation of both. Nucleation and growth of 6 tri gers B the dissolution of the metastable 7” phase which serves as the Niobium eeding source for further S growth. The 1800F (982C) starting condition contained a substantial amount of S which ties up much of the available Niobium in the alloy, limiting the amount of 7” that can form. As the amount of 6 increases, the hardness of the alloy decreases due to decreasing amounts of 7”. Superalloy 718-Metallurgy and Applications Edited by E.A. Loria The Minerals, Metals & Materials Society, 1989
15 citations
TL;DR: In this paper, the effect of post-heat treatment on the properties of nano particulate reinforced metal composites obtained by laser additive manufacturing (AM) processes has been studied, and it was found that nano particles can effectively strengthen the metal matrix under both as-built and heat-treated conditions, and the material undergoes static recrystallization during the post heat treatment.
Abstract:
To strengthen the metal components by selective laser melting (SLM), adding reinforcement particles and applying post treatments are generally regarded as the two effective means. However, how post heat treatment affects the properties of nano particulate reinforced metal composites obtained by laser additive manufacturing (AM) processes has rarely been studied. In this study, Inconel 718 matrix composite reinforced by 0.5 wt% nano TiC particles was prepared using SLM. To evaluate the effect of the heat treatment routines on the performance of the SLM-produced composite, two levels of solution temperature (980 and 1100 °C) were designed, and the solution treatment was followed by a standard two-step aging (720 °C for 8 h and 620 °C for 8 h). Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) observations were performed to examine the microstructure, and transmission electron microscopy (TEM) observation was conducted to characterize the morphologies of incorporated nano particles and precipitated phases. Tensile tests were conducted to evaluate the mechanical properties of the formed composites. It was found that nano particles can effectively strengthen the metal matrix under both as-built and heat-treated conditions, and the material undergoes static recrystallization during the post heat treatment. Also, it was discovered that nano TiC particles play an important role in refining the microstructure of Inconel 718 composite below 980 °C. The maximum tensile strength of 1370 MPa was observed under 980 °C + aging condition, representing a 16% increase as compared with the unreinforced Inconel 718.
15 citations
24 Jan 2018
TL;DR: In this paper, the influence of Nb on the precipitation and tensile properties of cast alloy IN625 is investigated and the results show that the δ phase is easy to precipitate after long-term aging at 700 °C (the service temperature of A-USC power plants).
Abstract: Cast alloy IN625 is a candidate Ni-base alloy for advanced ultra-supercritical (A-USC) power plants The aim of this study was to investigate the influences of Nb on δ phase precipitation and the tensile properties in this alloy The results show that the δ phase is easy to precipitate after long-term aging at 700 °C (the service temperature of A-USC power plants) and it is strongly affected by the content of Nb in the alloy The strength of alloys after aging at 700 °C for 10,000 h increases with the increasing Nb content and also increases sharply when compared to that of as-heat-treated alloys The increase in strength is found to be primarily associated with the precipitation of the δ phase
15 citations
Cites background from "Precipitation of the δ-Ni 3 Nb phas..."
...The normal form of the δ phase generally nucleates at grain boundaries, but at relatively high temperatures (850–900 ◦C) also forms in an intragranular fashion [19,23]....
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References
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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.
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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
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
01 Jan 1971-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
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