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 Tensile Deformation and Fracture Behaviors of a Nickel-Based Superalloy via In Situ Digital Image Correlation and Synchrotron Radiation X-ray Tomography

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2461 ◽  
Author(s):  
Qiang Zhu ◽  
Gang Chen ◽  
Chuanjie Wang ◽  
Heyong Qin ◽  
Peng Zhang
Keyword(s):  
Mechanical Properties ◽  
Synchrotron Radiation ◽  
Digital Image Correlation ◽  
Tensile Deformation ◽  
Image Correlation ◽  
X Ray ◽  
Nickel Based Superalloy ◽  
Deformation And Fracture ◽  
Fracture Behaviors

Nickel-based superalloys have become key materials for turbine disks and other aerospace components due to their excellent mechanical properties at high temperatures. Mechanical properties of nickel-based superalloys are closely related to their microstructures. Various heat treatment processes were conducted to obtain the desired microstructures of a nickel-based superalloy in this study. The effect of the initial microstructures on the tensile deformation and fracture behaviors was investigated via in situ digital image correlation (DIC) and synchrotron radiation X-ray tomography (SRXT). The results showed that the size and volume fraction of γ″ and γ′ phases increased with the aging time. The yield strength and the ultimate tensile strength increased due to the precipitation strengthening at the expense of ductility. The surface strain analysis showed severely inhomogeneous deformation. The local strains at the edge of specimens were corresponded to higher void densities. The fracture of carbides occurred owing to the stress concentration, which was caused by the dislocation accumulation. The fracture mode was dimple coalescence ductile fracture.

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.

scholarly journals In Situ Observation on Rate-Dependent Strain Localization of Thermo-Induced Shape Memory Polyurethane

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 982 ◽  
Author(s):  
Jian Li ◽  
Qianhua Kan ◽  
Kaijuan Chen ◽  
Zhihong Liang ◽  
Guozheng Kang
Keyword(s):  
Shape Memory ◽  
Heat Generation ◽  
Strain Localization ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Image Correlation ◽  
Mechanical Coupling ◽  
Convection Condition ◽  
Shape Memory Polyurethane

In situ monotonic tensile experiments of thermo-induced shape memory polyurethane (SMPU) at different loading rates were carried out by the digital image correlation (DIC) method and infrared camera FLIR®-A655sc in natural convection (NC) and forced convection (FC) conditions, respectively. The multiform strain localization of SMPU was observed by the DIC method, and the influence of thermo–mechanical coupling on the strain localization was analyzed by using the FLIR to measure the temperature field caused by the internal heat generation. The experimental results show that the strain localization mode strongly depends on the strain rate and convection condition, and the strain localization mode can be transformed by changing the convection condition from NC to FC. The competition mechanism between the strain hardening induced by the increasing loading rate and strain softening induced by the internal heat generation is indicated, the transition modes of strain localization are clarified, and the influences of thermo–mechanical coupling on shape memory effect are discussed.

scholarly journals Fracture mechanism of the δ phase in tensile deformation of a nickel-based superalloy

2020 ◽  
Vol 16 ◽  
pp. 102908
Author(s):  
Qiang Zhu ◽  
Gang Chen ◽  
Chuanjie Wang ◽  
Heyong Qin ◽  
Peng Zhang
Keyword(s):  
Fracture Mechanism ◽  
Tensile Deformation ◽  
Nickel Based Superalloy ◽  
Δ Phase

Deformation Behaviour of TRIP Steel Monitored by In Situ Neutron Diffraction

2014 ◽  
Vol 939 ◽  
pp. 25-30
Author(s):  
Jozef Zrník ◽  
Ondrej Muránsky ◽  
Petr Sittner
Keyword(s):  
Neutron Diffraction ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Deformation Behaviour ◽  
Tensile Load ◽  
Ferrite Matrix ◽  
Granular Bainite

The paper presents results ofin-situneutron diffraction experiments aimed on monitoring the phase evolution and load distribution in transformation induced plasticity (TRIP) steel when subjected to tensile loading. Tensile deformation behaviour of two TRIP-assisted multiphase steel with slightly different microstructures resulted from different thermo-mechanical treatments applied was investigated byin-situneutron diffraction. The steel with lower retained austenite volume fraction (fγ=0.04) and higher volume fraction of needle-like bainite in the α-matrix exhibits higher yield stress (sample B, 600MPa) but considerably lower elongation in comparison to the steel with higher austenite volume fraction (fγ=0.08), granular bainite and ferrite matrix (sample A, 500 MPa). The neutron diffraction results showed that the applied tensile load is redistributed at the yielding point in a way that the retained austenite bears a significantly larger load than the α-matrix during the TRIP steel deformation. Steel sample with higher volume fraction of retained austenite and less strong ferrite matrix proved to be a better TRIP steel with respect to strength, ductility and the side effect of the strain induced austenite-martensite transformation. The transforming retained austenite in time of loading provides potential for higher ductility of experimental TRIP steel but at the same time acts as a reinforcement phase during the further plastic deformation.TRIP steel, austenite conditioning, austenite transformation, structure, retained austenite, tensile deformation, neutron diffraction, load partitioning, mechanical properties.

scholarly journals Alignment of sample position and rotation during in situ synchrotron X-ray micro-diffraction experiments using a Laue cross-correlation approach

2019 ◽  
Vol 52 (5) ◽  
pp. 1119-1127 ◽  
Author(s):  
Chenglu Zhang ◽  
Yubin Zhang ◽  
Guilin Wu ◽  
Wenjun Liu ◽  
Ruqing Xu ◽  
...  
Keyword(s):  
Tensile Deformation ◽  
Three Dimensional ◽  
Surface Region ◽  
Image Correlation ◽  
Polycrystalline Materials ◽  
X Ray ◽  
Sample Rotation ◽  
Average Grain Size ◽  
Sample Position

Laue micro-diffraction has proven to be able to reveal material properties at the sub-grain scale for many polycrystalline materials and is now routinely available at several synchrotron facilities, providing an approach for nondestructive three-dimensional probing of the microstructures and mechanical states of materials. However, for in situ experiments, maintaining the positioning of the sample throughout the experiment, to achieve a good alignment of the characterized volumes, is a challenging issue. The aim of the present work is to address this problem by developing an approach based on digital image correlation of focused-beam Laue diffraction patterns. The method uses small changes in the diffraction signal as a focused X-ray beam is scanned over a surface region to allow corrections to be made for both sample lateral movement and rotation. The method is demonstrated using a tensile deformation experiment on an Al sample with 2.5 µm average grain size. The results demonstrate an accuracy of 0.5 µm for sample position registration and a precision in sample rotation of ∼0.01°. The proposed method is fast to implement and does not require the use of additional surface markers.

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.

Deformation Behaviour of TRIP Steel Monitoring by in-Situ Neutron Diffraction

2011 ◽  
Vol 465 ◽  
pp. 390-394 ◽  
Author(s):  
Jozef Zrník ◽  
Ondrej Muránsky ◽  
Petr Šittner ◽  
E.C. Oliver
Keyword(s):  
Neutron Diffraction ◽  
Trip Steel ◽  
Retained Austenite ◽  
Volume Fraction ◽  
Tensile Deformation ◽  
Deformation Behaviour ◽  
Tensile Load ◽  
Phase Evolution ◽  
In Situ Neutron Diffraction

The paper presents results of in-situ neutron diffraction experiments aimed on monitoring the phase evolution and load distribution in TRIP steel when subjected to tensile loading. Tensile deformation behaviour of TRIP steel with different initial microstructures showed that the applied tensile load is redistributed at the yield point and the harder retained austenite (Feγ) bears larger load then ferrite (Feα) matrix. After load partioning is finished, macroscopic yielding comes through simultaneous activity of the martensite transformation (in the austenite) and plastic deformation process in ferrite. The steel with higher volume fraction of retained austenite and less stronger ferrite appears to be a better TRIP steel having efficient structure for better plasticity purpose.

Sign in / Sign up

Export Citation Format

Share Document