Mechanism of plastic deformation of a Ni-based superalloy for VHTR applications

Mo, Kun; Lovicu, Gianfranco; Chen, Xiang; Tung, Hsiao Ming; Hansen, Jon B.; Stubbins, James F.

doi:10.1016/j.jnucmat.2013.03.083

Cited by 52 publications

(18 citation statements)

References 39 publications

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“…An anomaly is also present in this case at temperatures near to 600 • C, where a significant decrease in the elongation occurs. This anomalous behavior in the tensile properties at temperatures close to 600 • C was also evidenced by other authors [4,5,[13][14][15][16][17][18][19][20] and depends on the strain rate applied in the test. According to these researches, at a strain rate less than 10 −5 s −1 , this anomalous behavior is no longer observed, resulting in a constant drop in the yield strength and a constant ductility increase with the tensile test temperature increase.…”

Section: Tensile Testssupporting

confidence: 82%

Mechanical Behavior of Inconel 625 at Elevated Temperatures

Oliveira

Couto

Almeida

et al. 2019

Metals

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Inconel 625 is a nickel-based alloy that is mainly used in high-temperature applications. Inconel 625 exhibits an unstable plastic flow at elevated temperatures characterized by serrated yielding, well-known as the Portevin-Le Chatelier effect. The evaluation of the mechanical properties of Inconel 625 at high temperatures is the aim of this work. The tensile tests were executed in temperatures ranging from room temperature to 1000 °C with strain rates of 2 × 10−4 to 2 × 10−3 s−1. The creep tests were executed in the temperature range of 600–700 °C and in the stress range of 500–600 MPa in a constant load mode. The optical and scanning electron microscopes were used for surface fracture observation. In the curves obtained at 200–700 °C the serrated stress-strain behavior was observed, which was related to the dynamic strain aging effect. The yield strength and the elongation values show anomalous behavior as a function of the test temperature. An intergranular cracking was observed for a specimen tensile tested at 500 °C that can be attributed to the decohesion of the carbides along the grain boundaries. The fracture surface of the specimen tensile tested at 700 °C showed the predominance of transgranular cracking with tear dimples with a parabolic shape.

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Section: Tensile Testssupporting

confidence: 82%

Mechanical Behavior of Inconel 625 at Elevated Temperatures

Oliveira

Couto

Almeida

et al. 2019

Metals

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“…Although the tensile tests were stopped periodically in order to measure responses at different axial positions at the same load, the stress-strain curves were smooth with the exception of the curve of 300°C. The serrations in the stress-strain diagram at 300°C were ascribed to dynamic strain aging (DSA) [29,30]. The DSA in an RAFM steel has been reported at the intermediate temperature around 650 K, similar temperature to the current study [31].…”

Section: Methodssupporting

confidence: 65%

Load partitioning between ferrite/martensite and dispersed nanoparticles of a 9Cr ferritic/martensitic (F/M) ODS steel at high temperatures

Zhang

Miao

et al. 2015

Materials Science and Engineering: A

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a b s t r a c tIn this study, a high-energy synchrotron radiation X-ray technique was used to investigate the tensile deformation processes of a 9Cr-ODS ferritic/martensitic (F/M) steel at different temperatures. Two minor phases within the 9Cr-ODS F/M steel matrix were identified as Y 2 Ti 2 O 7 and TiN by the high-energy X-ray diffraction, and confirmed by the analysis using energy dispersive X-ray spectroscopy (EDS) of scanning transmission electron microscope (STEM). The lattice strains of the matrix and particles were measured through the entire tensile deformation process. During the tensile tests, the lattice strains of the ferrite/ martensite and the particles (TiN and Y 2 Ti 2 O 7 ) showed a strong temperature dependence, decreasing with increasing temperature. Analysis of the internal stress at three temperatures showed that the load partitioning between the ferrite/martensite and the particles (TiN and Y 2 Ti 2 O 7 ) was initiated during sample yielding and reached to a peak during sample necking. At three studied temperatures, the internal stress of minor phases (Y 2 Ti 2 O 7 and TiN) was about 2 times that of F/M matrix at yielding position, while the internal stress of Y 2 Ti 2 O 7 and TiN reached about 4.5-6 times and 3-3.5 times that of the F/M matrix at necking position, respectively. It indicates that the strengthening of the matrix is due to minor phases (Y 2 Ti 2 O 7 and TiN), especially Y 2 Ti 2 O 7 particles. Although the internal stresses of all phases decreased with increasing temperature from RT to 600°C, the ratio of internal stresses of each phase at necking position stayed in a stable range (internal stresses of Y 2 Ti 2 O 7 and TiN were about 4.5-6 times and 3-3.5 times of that of F/M matrix, respectively). The difference between internal stress of the F/M matrix and the applied stress at 600°C is slightly lower than those at RT and 300°C, indicating that the nanoparticles still have good strengthening effect at 600°C.

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“…1(c)). 11 When lower strain rates are used at elevated temperature, small cracks in the grain bounderies due to the embrittlement mentioned earlier, becomes the dominant fracture micromechanism and some times it is assited by DRX (Fig. 1(d)).…”

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confidence: 89%

“…In Alloy 617 nano-sized DRX has been observed locally at grain bounderies in front of cracks at lower strain rates ( 10 −5 s −1 and 10 −6 s −1 ) and elevated temperatures. 18 DRX has been found in Alloy 617 by others, 11,19 in highly strained areas 11 at temperatures above 800 • C when using a strain rate of 10 −3 s −1 and it has been found in creep deformed Alloy 617 at temperatures above 1 000 • C. 20 However, it seems that DRX may appear at lower temperatures than 800 • C during slow deformation, but restricted to grain bounderies, and seems to affect the fracture behaviour. 16…”

mentioning

confidence: 95%

“…The serrated yielding comes from pinning and unpinning of dislocations by solute interstitials and substitutional atoms, at lower and higher temperatures respectivly, denoted Portevin-Le Châtelier (PLC) effect. [6][7][8][9][10][11][12][13] Strain rate and temperature are influencing DSA, because the dislocation movement rate is influenced by deformation rate and temperature; temperature also influences the diffusion rate of the solute atoms. 6,[11][12][13] None of the tested materials showed DSA at RT, but both materials showed DSA at elevated temperatures for all tested strain rates.…”

mentioning

confidence: 99%

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Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature

Calmunger

Chai

Johansson

2014

Theoretical and Applied Mechanics Letters

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In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650 • C.Energy production by power plants must be more efficient to meet the increasing energy consumption. A higher efficiency can be established by increasing temperature and pressure in the boiler sections. This gives higher demands on the materials that should operate within these power plants. Not only is great high-temperature corrosion resistance of importance but also the mechanical behaviour during slow deformation because these alloys can undertake low deformation rates from 10 −5 s −1 (low cycle fatigue) to 10 −7 s −1 (creep) during service. 1,2 Current study was focused on damage and fracture micromechanisms related to low strain rate and high-temperature in two austenitic materials. Using uniaxial slow strain rate tensile testing (SSRT) at high-temperatures, the influence of low strain rates on these mechanisms could be investigated. Also precipitation due to high-temperature and deformation could be coupled to the damage and fracture behaviours.The austenitic stainless steel, AISI 316L and the nickel-base alloy, Alloy 617 were used in this study. Both types were solution treated before testing, AISI 316L at 1 050 • C for 10 min and Alloy 617 at 1 175 • C for 20 min. Table 1 shows the chemical composition of the materials.For the SSRT a Roell-Korthaus and an Instron 5982 tensile test machines were employed. The tensile test machines were equipped with a MTS 653 furnace and Magtec PMA-12/2/VV7-1 a) Corresponding author.

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Mechanism of plastic deformation of a Ni-based superalloy for VHTR applications

Cited by 52 publications

References 39 publications

Mechanical Behavior of Inconel 625 at Elevated Temperatures

Mechanical Behavior of Inconel 625 at Elevated Temperatures

Load partitioning between ferrite/martensite and dispersed nanoparticles of a 9Cr ferritic/martensitic (F/M) ODS steel at high temperatures

Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature

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