Suzuki segregation in Co–Ni-based superalloy at 973 K: An experimental and computational study by phase-field simulation

Koizumi, Yuichiro; Nukaya, Takeshi; Suzuki, S.; Kurosu, Shingo; Li, Yunping; Matsumoto, Hiroaki; Sato, Kazuhisa; Tanaka, Yuji; Chiba, Akihiko

doi:10.1016/j.actamat.2012.01.054

Cited by 87 publications

(26 citation statements)

References 28 publications

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“…11,21 On the other hand, the Suzuki segregation of alloying elements itself can serve as an important additional factor in strengthening superalloys at elevated temperatures. [16][17][18] Herein, we obtain an extremely hard nanoscale γ′ phase of Ni 3 X (X= Al, Nb or Ti) in a cobalt-based superalloy composed of 35% Ni, 3% Nb, 2% Al and 0.8% Ti (mass%) and demonstrate that a high density of stacking-fault ribbons can be formed in alloy matrix after cold working and aging at 1023 K as a result of significant Suzuki segregation (Supplementary Figure 1). These results open a new avenue for producing superalloys with 1 extremely high structural thermostability and exceptional mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

“…[16][17][18][19][20] On one hand, the formation of ribbons is energetically preferred because these planar defects lower the stacking-fault energy of the alloys. 17 Furthermore, the rich alloy elements in the ribbons (for example, Mo and Cr in Co-Ni-Cr-Mo alloys) hamper the diffusion of the major elements in the γ′ phase (Ni, Al) across the planar defects, thereby isolating individual γ′ phase nanoparticles. 11,21 On the other hand, the Suzuki segregation of alloying elements itself can serve as an important additional factor in strengthening superalloys at elevated temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Regulating the coarsening of the γ′ phase in superalloys

Bian

et al. 2015

NPG Asia Mater

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The properties of superalloys are typically deteriorated by the coarsening of the nano-sized γ′ phase, which is the primary strengthening component at high temperatures. Stabilizing the γ′ phase represents one of the key challenges in developing next-generation superalloys. Herein, we fabricate a cobalt-nickel-based superalloy with a nanoscale coherent γ′ phase, (Ni,Co) 3 (Al,Ti,Nb), which is isolated by stacking-fault ribbons in the alloy matrix as a result of the Suzuki segregation of alloying atoms. Additionally, we demonstrate that this new nanostructure can slow down the coarsening of the γ′ phase at high temperatures. As a result, the cobalt-nickel-based superalloy displays considerably high tensile yield points, exceeding 1650 MPa at room temperature and 1250 MPa at 973 K, which are markedly higher than those of the commonly used nickel-and cobalt-based superalloys. This study thereby paves a new path for developing superalloys with exceptional mechanical performance and thermal stability. INTRODUCTIONGeometrically close-packed and coherent A 3 B-type (A = Ni, Co; B = Al, Ti, and so on) γ′ phases exist in various high-temperature superalloys, and this substantially affects their mechanical performance. 1,2 One of the most critical issues currently restraining the service life of these superalloys lies in the coarsening of the nanoscale γ′ phase upon exposure to high temperatures. To date, much effort has been devoted to probing the morphology of the γ′ phase and to clarifying its coarsening mechanism upon aging in cobalt-and nickel-based superalloys. 3-9 It has been predicted by the Lifshitz-Slyozov-Wagner model 10,11 that coarsening of the γ′ phase in superalloys follows the general relationship r 3 = kt, where r is γ′ phase particle radius, t is the aging time and k is the coarsening-related rate constant.In general, the coarsening of the γ′ phase in superalloys is a diffusion process where large particles grow at the expense of smaller ones in the alloy matrix; this is termed Ostwald ripening. [12][13][14] The factors that predominantly control the coarsening rate of the γ′ phase include the γ/γ′ phase interfacial energy, the solubility of the γ′ phase in the γ phase and the diffusion coefficient of the constituent elements of the γ′ phase through either the γ/γ′ phase interface or the γ phase matrix. 15 Typical values of the interfacial energy of the γ/γ′ phase have been clearly demonstrated to be~20 mJ m − 2 , 15 a value that is very low and essentially remains stable. In addition, for a given material system, the solubility of small γ′ phase particles and the diffusion coefficient of the constituent elements of the γ′ phase in the

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Regulating the coarsening of the γ′ phase in superalloys

Bian

et al. 2015

NPG Asia Mater

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“…On the other hand, Koizumi at al [13] have shown that extended SFs are produced in the fcc phase of Co-Ni based superalloys when Nb is added in excess of 2% and following static annealing. Phase field simulation by the same authors has suggested that elements such as Co, Cr, Nb and Mo would have greater affinity for SFs when compared to Ni.…”

Section: Introductionmentioning

confidence: 99%

Segregation at stacking faults within the γ′ phase of two Ni-base superalloys following intermediate temperature creep

Viswanathan

Shi

Genç³

et al. 2015

Scripta Materialia

110

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“…The evidence of a decrease in the fault energies due to the solute segregation is also reported in the recent literature(Apostol and Mishin, 2011;Koizumi et al, 2012). Now, questions may arise regarding whether the observed trend in the Co-influenced γ surface are indeed representative of the inherent material properties(Ngan, 1995).…”

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confidence: 62%