In situ SANS investigation of the kinetics of rafting of γ′ precipitates in a fourth-generation single-crystal nickel-based superalloy

Ratel, N.; Demé, Bruno; Bastie, P.; Caron, Pierre

doi:10.1016/j.scriptamat.2008.07.031

Cited by 21 publications

(9 citation statements)

References 9 publications

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“…0 rafting can also occur under purely thermal treatment without the simultaneous presence of an external load (Veron et al, 1996;Matan et al, 1999;Henderson et al, 1999) in cases where the specimens have been predeformed either plastically (Veron et al, 1996) or by creep (Matan et al, 1999;Henderson et al, 1999) at relatively low temperature. It was found, using in situ small-angle neutron scattering (SANS) (Veron & Bastie, 1997;Ratel et al, 2008), that rafting can occur if a certain threshold for creep strain is exceeded during the pre-deformation. The results point to an anisotropic arrangement of dislocations in the pre-deformed specimens, which leads then to the observed formation of 0 rafts at high temperature (HT).…”

Section: Introductionmentioning

confidence: 99%

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In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

et al. 2011

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Exposure of a superalloy to an external load results in anisotropic coarsening of the 0 precipitates, so-called rafting. It was reported in the past that 0 rafting can also occur as a result of purely thermal treatment, without the simultaneous presence of an external load, if the specimen has been pre-deformed at relatively low temperature. The evolution of 0 morphology in pre-deformed specimens of SCA425 Ni-base superalloy was examined in the present study. Unlike in the previous experiments, the compressive stress was used for prestraining. In situ small-angle neutron scattering (SANS) was employed, which enabled the determination of the morphology directly at high temperature. Both for strong and for weak pre-straining, rounding of the originally cuboidal precipitates towards an ellipsoidal shape on heating was observed. Weak prestraining (0.1, 0.5%) does not cause rafting on subsequent heating. On the other hand, the detailed evaluation of SANS data provides some indication of rafting during the subsequent heating after severe compressive pre-straining (2%). The experiment indicates the role of dislocation rearrangement at the matrix/ precipitate interface during pre-straining. research papers 940 Pavel Strunz et al. 0 precipitates in pre-deformed Ni-base superalloy J. Appl. Cryst. (2011). 44, 935-944 Figure 6Central area of the scattering curve for the sample pre-strained at 1223 K (a) after 20 min at 1323 K and (b) after 6.5 h at 1323 K. The intensities are plotted in logarithmic scale.

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Section: Introductionmentioning

confidence: 99%

“…Unlike in the studies of Veron & Bastie (1997) and Ratel et al (2008) performed on AM1 superalloy (around 70% precipitate volume fraction at room temperature, RT), we used compressive stress for pre-straining the SCA425 samples. The motivation for the choice of compression is twofold.…”

Section: Introductionmentioning

confidence: 99%

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

et al. 2011

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“…It is well known that the microstructure of Ni-based single-crystal (SX) superalloys consists of two phases: ordered intermetallic c 0 precipitates with an L1 2 structure coherently embedded in a disordered face-centered cubic (fcc) c matrix [1][2][3][4]. Because of this unique microstructure, superalloys exhibit unique temperature-dependent strength properties under simple monotonic loading [2][3][4][5][6].…”

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confidence: 99%

“…Because of this unique microstructure, superalloys exhibit unique temperature-dependent strength properties under simple monotonic loading [2][3][4][5][6]. On the other hand, because these superalloy components are subjected to cyclic thermal stresses resulting from startup and shutdown, mechanical fatigue has been an area of ever-growing interest for the past several decades [7][8][9][10].…”

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confidence: 99%

Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

et al. 2015

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“…Rafting (which is a preferential coarsening) in nickel alloy is essentially a phenomenon about morphological instabilities, which leads to the destruction of an initially periodical arrangement of precipitates during service and eventually causes the formation of regular coarsening structure. Rafting can bring about either hardening or softening of the microstructure [3][4][5][6][7]. The kinetics of directional coarsening is affected by the type of the applied stress (tensile or compression condition), the sign and magnitude of the γ / γ' lattice misfit, and the difference in the elastic constants of the two phases [7,9].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional phase field simulation for rafting of multiparticle precipitate in elastic inhomogeneous alloy under external stress

Mao

Kong

Shuai

et al. 2019

J min metall B Metall

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Nickel-based super alloys are the main candidate materials for aero-engines, gas turbine blades etc. This paper focuses on the simulation of nucleation and growth kinetics of γ' phase, and stress response mechanism of γ' phase particles during their preferential coarsening (rafting) in elastic inhomogeneous system. A phase-field model is employed in the present study, which incorporates chemical, interfacial, and elastic energies, and it couples essentially to externally imposed mechanical field. Due to the limitations of the 2D model on analyzing the shape and size of the precipitate particles, the process of γ' phase particles growing and coarsening is further modeled by performing 3D simulation. The results show that the average particle size is linearly related to the evolution time and satisfies the Lifshitz-Slyozov-Wagner (LSW) classical coarsening theory when the external stress is not applied. Particles exhibit a strong special orientation under tensile stress, and the orientation is in excellent agreement with previous studies. In the nucleation stage, the collision and coalescence between particles promote rafting significantly, and the number of soft particles is obviously larger than that of hard particles. In the coarsening stage, the growth rate of soft particles is higher than that of hard particles. Three-dimensional simulation results show that the effect of final characteristic size of precipitated particles is not significant by external loads. The morphology evolution and coarsening mechanism of the precipitated particles are of great significance for studying the strengthening mechanism of super-alloy.

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In situ SANS investigation of the kinetics of rafting of γ′ precipitates in a fourth-generation single-crystal nickel-based superalloy

Cited by 21 publications

References 9 publications

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

In situobservation of morphological changes of γ′ precipitates in a pre-deformed single-crystal Ni-base superalloy

Deformation mechanisms of a nickel-based single-crystal superalloy during low-cycle fatigue at different temperatures

Three-dimensional phase field simulation for rafting of multiparticle precipitate in elastic inhomogeneous alloy under external stress

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