The Effects of Thermal History on Toughness of Ni-Based Corrosion Resistant Alloys During In-Situ Hydrogen Charging

2021 ◽  
Author(s):  
Michelle Kent ◽  
Kip Findley
Keyword(s):  
Thermal History ◽  
Potential Drop ◽  
Heat Treatments ◽  
Alloy 718 ◽  
Unstable Crack ◽  
Heat Treated ◽  
Δ Phase ◽  
Incremental Step ◽  
M23c6 Carbides

Abstract Hydrogen embrittlement (HE) susceptibility was investigated for Alloy 718 and Alloy 945X specimens heat treated to a set of conditions within the specifications of API Standard 6ACRA. Heat treatments were selected to simulate the potential variation in thermal history in thick sections of bar or forged products and produce various amounts of discontinuous grain boundary δ phase in Alloy 718 and M23C6 carbides in Alloy 945X, while maintaining a constant hardness in the range of 35-45 HRC for Alloy 718 and 34-42 HRC for Alloy 945X. Time-temperature-transformation (TTT) diagrams and experimentation were used to select a set of heat treatments containing no δ phase, a small quantity of δ, and a larger quantity of δ in Alloy 718. The presence of δ phase has not been verified for the moderate condition. A similar approach was taken regarding M23C6 carbides in Alloy 945X. Incremental step loading (ISL) tests were conducted under in-situ cathodic charging on circular notch tensile (CNT) specimens in a 0.5 M H2SO4 solution. During the test, the direct current potential drop (DCPD) was measured across the notch to determine the stress intensity associated with unstable crack growth. Results indicate that even very small quantities of δ phase in Alloy 718 are detrimental to HE resistance. Both Alloy 718 and Alloy 945X show decreases in HE resistance with aging, with a greater degradation in Alloy 718.

Recrystallization and Grain Growth during Alloy 718 Processing

2007 ◽  
Vol 539-543 ◽  
pp. 3094-3099
Author(s):  
Nho Kwang Park ◽  
Jeoung Han Kim ◽  
Jong Taek Yeom
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Heat Treatments ◽  
Grain Structure ◽  
Alloy 718 ◽  
Compression Tests ◽  
Δ Phase ◽  
Grain Boundary Characteristics ◽  
The Difference ◽  
Boundary Characteristics

In Alloy 718 ingot cogging process, dynamic and metadynamic recrystallizations, and static grain growth occur, and also the presence of δ phase plays a key role in controlling the grain size. In this study, the evolution of grain structure in VIM/VAR-processed Alloy 718 ingots during post-cogging heat treatments is dealt with. Compression tests were made on VIM/VAR-processed Alloy 718 ingot at temperatures between 900oC ~ 1150oC. Heat treatments were made on the compression-tested specimens, and the variation of grain size was evaluated. Constitutive equations for the grain growth are established to represent the evolution of microstructures. Special attention is paid to the evolution of grain structure under the condition of dynamic and metadynamic recrystallizations, and grain growth. The grain growth rate depends mainly on the presence of δ-phase below the δ-solvus temperature, and on the difference in the grain boundary characteristics above it.

scholarly journals Influence of Interstitials Content on the Diffusion of Niobium in Alloy 718

2009 ◽  
Vol 289-292 ◽  
pp. 161-166 ◽  
Author(s):  
Benoît Ter-Ovanessian ◽  
Cedric Berrest ◽  
Julien Deleume ◽  
Jean Marc Cloué ◽  
Eric Andrieu
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Phase Evolution ◽  
Inert Atmosphere ◽  
Solid Solution Hardening ◽  
Physical Metallurgy ◽  
Alloy 718 ◽  
Heat Treated ◽  
Δ Phase ◽  
And Diffusion

Many studies have emphasized the beneficial effect of niobium on the physical metallurgy of Ni-Cr-Fe alloy 718. Among the different strengthening actions of niobium, such as solid solution hardening and carbide precipitation, the precipitation of niobium with nickel in a strengthening phase γ” (Ni3Nb) during the aging heat treatment has the largest influence on the mechanical properties of alloy 718. The improvement of the niobium distribution and diffusion in the Ni-matrix may allow a more homogenized repartition of γ” precipitates and seems then to be an effective way to upgrade the mechanical properties. As γ” precipitates decompose to the stable δ phase at very long aging times, the study of the effect of carbon, nitrogen and oxygen concentrations on precipitation and dissolution of the δ phase may give information on γ” precipitation and on niobium distribution. It is the purpose of the present work to examine the role that the alloy content of interstitial species plays with the niobium-rich δ phase evolution in alloy 718. Alloy 718 samples were heat treated under hydrogenated argon at 980°C for 0 to 96 hours in order to gradually curb the content of interstitial species by reaction with the reducing atmosphere. Chemical analyses realized by glow discharge mass spectrometry (GDMS) confirmed the reduction of the concentration of these species. Specimens were solution-treated for 1h at 1050°C in an inert atmosphere and furnace cooled. Some of the samples were then aged at 920°C for times ranging from 10 min to 1 hour. The precipitation was measured quantitatively in terms of volume fraction and the morphology of the precipitates was appreciated using scanning electron microscopy (SEM). The differences in the precipitation kinetics and in the microstructure evolution for each interstitial concentration are then discussed.

scholarly journals Influence of Heat Treatments on Heat Affected Zone Cracking of Gas Tungsten Arc Welded Additive Manufactured Alloy 718

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 881 ◽  
Author(s):  
Raza ◽  
Hurtig ◽  
Asala ◽  
Andersson ◽  
Svensson ◽  
...  
Keyword(s):  
Heat Affected Zone ◽  
Hot Isostatic Pressing ◽  
Heat Treatments ◽  
Alloy 718 ◽  
Gas Tungsten Arc ◽  
Material Condition ◽  
Heat Treated ◽  
Maximum Crack ◽  
Material Conditions ◽  
Haz Cracking

The weldability of additive manufactured Alloy 718 was investigated in various heat-treated conditions. The microstructure of the base metal was examined in detail in order to understand the effect of different pre-weld heat treatments; i.e., solution, solution and aging, and hot isostatic pressing. After welding, the variation in total crack lengths, maximum crack length and the total number of cracks in the heat affected zone (HAZ) were used as criteria for the cracking susceptibility of each material condition where wrought Alloy 718 was used as the reference material. Selective laser melting (SLM) manufactured Alloy 718 was susceptible to HAZ cracking in all material conditions. Total crack lengths in HAZ were highest in the SLM as-built condition and lowest in the SLM hot isostatic pressed condition. The cracks that were found in the HAZ of the welded materials consisted of liquation cracks, with eutectic product surrounding the cracks, as well as cracks from which liquation products were absent.

scholarly journals The Effect of Hydrogen on the Nanoindentation Behavior of Heat Treated 718 Alloy

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1451
Author(s):  
Gaute Stenerud ◽  
Tarlan Hajilou ◽  
Jim Stian Olsen ◽  
Iman Taji ◽  
Afrooz Barnoush ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Nickel Superalloy ◽  
Heat Treatments ◽  
New Method ◽  
Solution Annealing ◽  
Anodic Potential ◽  
Heat Treated ◽  
Hardness Increase ◽  
Cathodic Charging

In this study, the effect of precipitates on the surface mechanical properties in the presence of hydrogen (H) is investigated by in situ electrochemical nanoindentation. The nickel superalloy 718 is subjected to three different heat treatments, leading to different sizes of the precipitates: (i) solution annealing (SA) to eliminate all precipitates, (ii) the as-received (AR) sample with fine, dispersed precipitates, and (iii) the over-aged (OA) specimen with coarser precipitates. The nanoindentation is performed using a conical tip, and a new method of reverse imaging is employed to calculate the nano-hardness. The results show that the hardness of the SA sample is significantly affected by H diffusion. However, it could be recovered by removing the H from its matrix by applying an anodic potential. Since the precipitates in the OA and AR samples are different, they are influenced by H differently. The hardness increase for the OA sample is more significant in −1200mV, while for the AR specimen, the H is more effective in −1500mV. In addition, the pop-in load is reduced when the samples are exposed to cathodic charging, and it cannot be fully recovered by switching to an anodic potential.

scholarly journals Multi-Dimensional Revealing the Influence Mechanism of the δ Phase on the Tensile Fracture Behavior of a Nickel-Based Superalloy on the Mesoscopic Scale

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 610
Author(s):  
Qiang Zhu ◽  
Linfu Zhang ◽  
Chuanjie Wang ◽  
Gang Chen ◽  
Heyong Qin ◽  
...  
Keyword(s):  
Strain Localization ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Ageing Time ◽  
Image Correlation ◽  
Tensile Fracture ◽  
Nickel Based Superalloy ◽  
Heat Treated ◽  
Δ Phase

As the key materials of aircraft engines, nickel-based superalloys have excellent comprehensive properties. Mircotensile experiments were carried out based on in situ digital image correlation (DIC) and in situ synchrotron radiation (SR) technique. The effects of the δ phase on the grain orientation, surface roughening, and strain localization were investigated. The results showed that the average kernel average misorientation (KAM) value of the fractured specimens increased significantly compared with that of the heat-treated specimens. The surface roughness decreased with an increasing volume fraction of the δ phase. The strain localization of specimens increased with the increasing ageing time. The size and volume fraction of voids gradually increased with the increase in plastic strain. Some small voids expanded into large voids with a complex morphology during micro-tensile deformation. The needle-like δ phase near the fracture broke into short rods, while the minor spherical δ phase did not break. The rod-like and needle-like δ phases provided channels for the propagation of the microcrack, and the accumulation of the microcrack eventually led to the fracture of specimens.

Influence of ion-milling on the T2 phase in Al-2.5%Li-2.5%Cu alloy

1989 ◽  
Vol 47 ◽  
pp. 288-289
Author(s):  
J. R. Reed ◽  
D. J. Michel ◽  
P. R. Howell
Keyword(s):  
Thin Foil ◽  
Icosahedral Symmetry ◽  
Ion Milling ◽  
Cu Alloy ◽  
Thin Foils ◽  
Heat Treated ◽  
Aluminum Solid Solution ◽  
In Situ Heating ◽  
The Stability

The Al6Li3Cu (T2) phase, which exhibits five-fold or icosahedral symmetry, forms through solid state precipitation in dilute Al-Li-Cu alloys. Recent studies have reported that the T2 phase transforms either during TEM examination of thin foils or following ion-milling of thin foil specimens. Related studies have shown that T2 phase transforms to a microcrystalline array of the TB phase and a dilute aluminum solid solution during in-situ heating in the TEM. The purpose of this paper is to report results from an investigation of the influence of ion-milling on the stability of the T2 phase in dilute Al-Li-Cu alloy.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimens were solution heat treated 1 h at 550°C and aged 1000 h at 190°C in air to develop the microstructure. The disc specimens were electropolished to achieve electron transparency using a 20:80 (vol. percent) nitric acid: methanol solution at -60°C.

3-D Characterization of Global and Local Microstructural Effects on Spall Damage in Shock Loaded FCC Metals: Experimental and Modeling

2013 ◽  
Author(s):  
A. Brown ◽  
K. Krishnan ◽  
L. Wayne ◽  
P. Peralta ◽  
S. N. Luo ◽  
...  
Keyword(s):  
Weak Link ◽  
Heat Treatments ◽  
Taylor Factor ◽  
Weak Links ◽  
Spall Damage ◽  
Heat Treated ◽  
Microstructural Effects ◽  
Global And Local ◽  
Low Pressures

Global and local microstructural weak links for spall damage were investigated using 3-D characterization in polycrystalline (PC) and multicrystalline (MC) copper samples, respectively. All samples were shocked via flyer-target plate experiments using a laser drive at low pressures (2–6 GPa). The flyer plates measured approximately 500 μm thick and 8 mm in diameter and the target plates measured approximately 1000 μm thick and 10 mm in diameter. Electron Backscattering Diffraction (EBSD) and optical microscopy were used to determine to presence of voids and relate them to the surrounding microstructure. Statistics on the strength of grain boundaries (GBs) was conducted by analyzing PC samples and collecting the misorientation across GBs with damage present, and it was found that a misorientation range of 25–50° is favorable for damage. Statistics were also taken of copper PC samples that had undergone different heat treatments and it was found that although the 25–50° range is less dominant, it is still favorable for damage nucleation. Removal of initial plastic strain via heat treatments and an increase in Σ3 CSL boundaries, indicative of strong annealing twins, also led to an increased amount of transgranular damage. 3-D X-ray tomography data were used to investigate the shape of the voids present in untreated, as received and heat treated samples. It was found that the as received sample contained a higher amount of “disk”, or, “sheet-like” voids indicative of intergranular damage, whereas the heat treated samples had a higher fraction of spherical shaped voids, indicative of transgranular damage. MC samples were used to study microstructural weak links for spall damage because the overall grain size is much larger than the average void size, making it possible to determine which GBs nucleated damage. Simulations and experimental analysis of damage sites with large volumes indicate that high Taylor factor mismatches with respect to the crystallographic grain GB normal is the primary cause for the nucleation of damage at a GB interface and a low Taylor factor along the shock direction in either grain drives void growth perpendicular to the GB. Cases where experimental results show damage and simulation results show no damage are attributed to the presence of an intrinsic microstructural weak link, such as an incoherent twin boundary.

The Use of In Situ Characterization Techniques for the Development of Intermetallic Titanium Aluminides

2014 ◽  
Vol 783-786 ◽  
pp. 2097-2102 ◽  
Author(s):  
Svea Mayer ◽  
Emanuel Schwaighofer ◽  
Martin Schloffer ◽  
Helmut Clemens
Keyword(s):  
Titanium Aluminides ◽  
Turbine Blades ◽  
Heat Treatments ◽  
Mechanical Processing ◽  
Tial Alloys ◽  
Solidification Processes ◽  
Consistent Picture ◽  
Aero Engines ◽  
Multi Phase

Urgent needs concerning energy efficiency and environmental politics require novel approaches to materials design. One recent example is thereby the implementation of light-weight intermetallic titanium aluminides as structural materials for the application in turbine blades of aero-engines as well as in turbocharger turbine wheels for the next generation of automotive engines. Each production process leads to specific microstructures which can be altered and optimized by thermo-mechanical processing and / or subsequent heat-treatments. To develop sound and sustainable processing routes, knowledge on solidification processes and phase transformation sequences in advanced TiAl alloys is fundamental. Therefore, in-situ diffraction techniques employing synchrotron radiation and neutrons were used for establishing phase fraction diagrams, investigating advanced heat-treatments as well as for optimizing thermo-mechanical processing. Summarizing all results a consistent picture regarding microstructure formation and its impact on mechanical properties in advanced multi-phase TiAl alloys can be given.

Rumen protection of heat-treated soybean proteins

1992 ◽  
Vol 72 (1) ◽  
pp. 71-81 ◽  
Author(s):  
B. M. Mosimanyana ◽  
D. N. Mowat
Keyword(s):  
Soybean Meal ◽  
Block Design ◽  
Soybean Proteins ◽  
Passage Rate ◽  
Heat Treated ◽  
Ruminal Degradation ◽  
In Situ Degradation ◽  
Exit Temperature ◽  
Forced Air

The effects of processing variables on soybean crude protein (CP) ruminal degradation were investigated. Soybean meal (SBM) was heated in a forced-air oven (90 °C, 1 h) with blood (0, 5, 10 and 20% dry matter) and/or xylose (3 mol mol−1 SBM-blood lysine) in a randomized complete block design. In another experiment, whole soybeans were utilized using the following treatments: raw; roasted (in Gem Co. unit exit temperature 150 °C) and steeped for 0 or 2 h; roasted, flaked (exit temperature 111 °C) and steeped for 0, 1, 2, 3 h or 1 h with 4% xylose and/or 10% blood. Solubility of SBM CP was reduced (P < 0.01) by the addition of xylose, without adverse effects on pepsin-digestible CP and acid detergent insoluble nitrogen. In situ degradation of CP (EDCP), assuming a passage rate of 5% h−1, of SBM was reduced by the addition of blood (P < 0.05) and particularly xylose (P < 0.01). Soybean CP solubility was reduced (P < 0.01) by roasting and flaking (65.6 vs. 17.6% total CP). Not flaking the roasted beans further reduced (P < 0.01) CP solubility (to 10.4%) probably due to less rapid cooling. The EDCP of raw soybeans (87.6%) was reduced by roasting (64.2%), steeping whole (57.6%) or flaked (61.1%) beans. These data support xylose to effectively reduce ruminal degradation of SBM and simple steeping (1 h) with or without flaking to further reduce EDCP of roasted soybeans. Key words: Soybean meal, soybeans, xylose, blood, steeping, protein degradation

Dlts-Studies on the “New Oxygen Donor” in Heat Treated and Hydrogenated CZ-Grown SI

1985 ◽  
Vol 59 ◽  
Author(s):  
Karlheinz Hölzlein ◽  
G. Pensl ◽  
M. Schulz ◽  
N. M. Johnson
Keyword(s):  
Low Temperature ◽  
Heat Treatments ◽  
Experimental Results ◽  
Interface Model ◽  
Trap States ◽  
High Concentration ◽  
Oxygen Donor ◽  
Heat Treated ◽  
Processing Steps

ABSTRACTCz-grown Si samples containing a high concentration of oxygen are investigated after various processing steps by DLTS. Heat treatments ranging from 500°C–1000°C are performed to study the formation and annihilation of the “New Oxygen Donor” (ND) traps. Hydrogenation at low temperature leads to a reduction of the ND trap states. The experimental results confirm the “SiOx Interface Model” which assumes two differing types of interfacerelated states.

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