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.

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.

The Effect of Post Weld Heat Treatment on Mechanical Properties of Friction-Welded Alloy 718 and SNCRW Stainless Steel

2007 ◽  
Vol 26-28 ◽  
pp. 511-514 ◽  
Author(s):  
Nam Yong Kim ◽  
Jeoung Han Kim ◽  
Yu Sik Kong ◽  
Jong Won Yoon ◽  
Jong Taek Yeom ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Weld Joint ◽  
Friction Welding ◽  
Rotation Speed ◽  
Post Weld Heat Treatment ◽  
Alloy 718 ◽  
Temperature Range ◽  
Heat Treated ◽  
Weld Heat

The effect of post weld heat treatment on mechanical properties of friction welded Alloy 718 and SNCRW was investigated. Friction welding tests were carried out at a constant rotation speed and pressure. Optimum friction condition was found to be the friction pressure of 25kg/cm2, friction time of 40sec, upset pressure of 80 kg/cm2, and dwell time of 5sec. After friction welding tests, post weld heat treatments were performed in the temperature range of 500-900°C for 8hrs in order to investigate the microstructure and mechanical properties of weld joint. Specimens with the post weld heat treatment at 720°C for 8hrs show optimal mechanical properties. Residual stress of post weld heat treated specimens was measured to weld joint in the same temperature range. After friction welding tests on samples with a diameter of 80mm, tensile properties of post-weld-heat-treated and non-heat-treated samples were compared.

EFFECT OF NI/TI RATIO ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF MO-DOPED NITIAL INTERMETALLICS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2694-2699 ◽  
Author(s):  
XIAOYUN SONG ◽  
YAN LI ◽  
SHUSUO LI
Keyword(s):  
Mechanical Properties ◽  
Yield Stress ◽  
Precipitation Hardening ◽  
Volume Fraction ◽  
Solid Solution Hardening ◽  
X Ray Diffraction ◽  
Hardening Effect ◽  
Rich Alloy ◽  
Increasing Temperature ◽  
Compressive Tests

The microstructures and mechanical properties of Ni 50- x Ti 43+ x Al 6 Mo 1 ( x = 0.5, 1, 1.5, 3.5, 5.5 and 7 at. %) alloys have been investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and compressive tests. We found that the variation of Ni / Ti ratio is the predominant reason for affecting the yield stress. The yield stress at room temperature of Ni -rich and Ti -rich alloys was higher than that of the equi-atomic alloy due to the strong solid solution hardening caused by the variation of Ni / Ti ratio. The size and volume fraction of Ti 2 Ni phase decreased with increasing Ni / Ti ratio. The yield stress at 600°C and 700°C increased with the increasing volume fraction of Ti 2 Ni phase due to the precipitation hardening effect. The precipitation hardening effect was weakened with increasing temperature. For the Ti -rich alloy deformed at 800°C, the yield stress deceased with the increasing of Ni / Ti ratio due to the reduced strength and unfavorable distribution of Ti 2 Ni .

scholarly journals Effect of SiC on Microstructure, Phase Evolution, and Mechanical Properties of Spark-Plasma-Sintered High-Entropy Ceramic Composite

Ceramics ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 359-371
Author(s):  
Hanzhu Zhang ◽  
Farid Akhtar
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Phase Evolution ◽  
Ceramic Composites ◽  
Hexagonal Structure ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Spark Plasma ◽  
Fcc Phase ◽  
Sic Composites

Ultra-high temperature ceramic composites have been widely investigated due to their improved sinterability and superior mechanical properties compared to monolithic ceramics. In this work, high-entropy boron-carbide ceramic/SiC composites with different SiC content were synthesized from multicomponent carbides HfC, Mo2C, TaC, TiC, B4C, and SiC in spark plasma sintering (SPS) from 1600 °C to 2000 °C. It was found that the SiC addition tailors the phase formation and mechanical properties of the high-entropy ceramic (HEC) composites. The microhardness and fracture toughness of the HEC composites sintered at 2000 °C were improved from 20.3 GPa and 3.14 MPa·m1/2 to 26.9 GPa and 5.95 MPa·m1/2, with increasing SiC content from HEC-(SiC)0 (0 vol. %) to HEC-(SiC)3.0 (37 vol. %). The addition of SiC (37 vol. %) to the carbide precursors resulted in the formation of two high-entropy ceramic phases with two different crystal structures, face-centered cubic (FCC) structure, and hexagonal structure. The volume fraction ratio between the hexagonal and FCC high-entropy phases increased from 0.36 to 0.76 when SiC volume fraction was increased in the composites from HEC-(SiC)0 to HEC-(SiC)3.0, suggesting the stabilization of the hexagonal high-entropy phase over the FCC phase with SiC addition.

Effects of Alloy Chemistry and Solidification Rate on the Mechanical Properties of an Al-9Si-1Cu Alloy for Powertrain Applications

2006 ◽  
Vol 519-521 ◽  
pp. 1727-1732 ◽  
Author(s):  
Daryoush Emadi ◽  
Robert Mackay ◽  
L.V. Whiting ◽  
Jerry Sokolowski ◽  
Mahi Sahoo
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Solidification Rate ◽  
Potential Candidate ◽  
Sand Cast ◽  
Automotive Components ◽  
Alloy Chemistry ◽  
Heat Treated ◽  
Lower Porosity ◽  
Engine Blocks

The potential use of an Al-9Si-1Cu alloy (W328 alloy) as a replacement for W319 alloy in engine blocks was investigated.. The ambient mechanical properties (tensile, hardness and fatigue) of sand and permanent mould cast test bars along with bars machined from a sand cast automotive component were studied. The tensile properties were evaluated in as-cast and T6 heat-treated conditions. The effects of Fe and Mn on properties were also investigated. The castings in W328 alloy exhibit lower porosity than W319 alloy, which is attributed to the smaller solidification range and feeding distance and larger volume fraction of the eutectic phase. Higher iron levels increased the level of intermetallics and reduced properties. The addition of Mn did not offset the effect of higher iron levels. The W328 alloy offers some advantages over the 319 alloy and is a potential candidate for production of automotive components such as engine blocks and cylinder heads.

Hot-die Forging of a β-stabilized γ-TiAl Based Alloy

2008 ◽  
Vol 1128 ◽  
Author(s):  
Wilfried Wallgram ◽  
Helmut Clemens ◽  
Sascha Kremmer ◽  
Andreas Otto ◽  
Volker Güther
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Small Deformation ◽  
High Volume ◽  
Compression Tests ◽  
Tial Alloys ◽  
Β Phase ◽  
Heat Treated ◽  
Hot Die Forging

AbstractBecause of the small “deformation window” hot-working of γ-TiAl alloys is a complex and difficult task and, therefore, isothermal forming processes are favoured. In order to increase the deformation window a novel Nb and Mo containing γ-TiAl based alloy (TNM™ alloy) was developed. Due to a high volume fraction of β-phase at elevated temperatures the alloy can be hot-die forged under near conventional conditions, which means that conventional forging equipment with minor and inexpensive modifications can be used. With subsequent heattreatments balanced mechanical properties can be achieved. This paper summarizes our progress in establishing a “near conventional” forging route for the fabrication of γ-TiAl components. The results of lab scale compression tests and forging trials on an industrial scale are included. In addition, the mechanical properties of forged and heat-treated TNM™ material are presented.

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.

scholarly journals Synthesis Route, Microstructural Evolution, and Mechanical Property Relationship of High-Entropy Alloys (HEAs): A Review

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3065
Author(s):  
Omoyemi Temitope Onawale ◽  
Prince Valentine Cobbinah ◽  
Rivel Armil Nzeukou ◽  
Wallace Rwisayi Matizamhuka
Keyword(s):  
Mechanical Properties ◽  
Phase Evolution ◽  
Dislocation Motion ◽  
Solid Solution Hardening ◽  
Engineering Properties ◽  
Initial Structure ◽  
High Entropy ◽  
Plasma Sintering ◽  
Dislocation Hardening ◽  
Spark Plasma

Microstructural phase evolution during melting and casting depends on the rate of cooling, the collective mobility of constituent elements, and binary constituent pairs. Parameters used in mechanical alloying and spark plasma sintering, the initial structure of binary alloy pairs, are some of the factors that influence phase evolution in powder-metallurgy-produced HEAs. Factors such as powder flowability, laser power, powder thickness and shape, scan spacing, and volumetric energy density (VED) all play important roles in determining the resulting microstructure in additive manufacturing technology. Large lattice distortion could hinder dislocation motion in HEAs, and this could influence the microstructure, especially at high temperatures, leading to improved mechanical properties in some HEAs. Mechanical properties of some HEAs can be influenced through solid solution hardening, precipitation hardening, grain boundary strengthening, and dislocation hardening. Despite the HEA system showing reliable potential engineering properties if commercialized, there is a need to examine the effects that processing routes have on the microstructure in relation to mechanical properties. This review discusses these effects as well as other factors involved.

Macroprobe Mode for the Study of Segregation in Steels

1990 ◽  
Vol 48 (2) ◽  
pp. 260-261
Author(s):  
Auclair Gilles ◽  
Benoit Danièle
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
High Performance ◽  
Volume Fraction ◽  
Sheet Steel ◽  
Acquisition Time ◽  
Chemical Information ◽  
X Ray ◽  
Accurate Quantitative Analysis ◽  
Optical Micrographs

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.

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