Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

Razumovskiǐ, I. M.; Razumovskiy, Vsevolod I.; Logachev, I. A.; Rodin, A. O.; Razumovsky, Mikhail

doi:10.1134/s0036029520110129

Cited by 4 publications

(10 citation statements)

References 8 publications

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“…Calculated values of the parameters E gb , η, and χ i for the segregation of refractory metals V, Cr, Zr, Nb, Mo, Ru, Hf, Ta, W, Re, and Ir on a special GB Σ 13[1 −1 0 0](1 1 −2 4) for the hcp phases of titanium are shown in Figure 1 [23]. It follows from Figure 1 that W, Ta, Re, Nb, Mo, and V contribute to the increase in the cohesive strength of both the α-matrix and the GB in titanium alloys with a hcp lattice.…”

Section: Titanium-based Alloysmentioning

confidence: 99%

“…According to the results of tests for long-term strength at high test temperatures T and long time-to-rupture (large values of the parameter P), the experimental alloy ST6U is compared in long-term strength with the alloy VT18U and still exceeds the alloy VT25U-for example, at a temperature of 800 • C under a load of 118 MPa. Judging by the nature of the change in the characteristics of lg(σ) − P in the Larson-Miller diagram [23,27], the ST6U alloy has greater structural stability compared to its analogues.…”

Section: Ti-based Alloysmentioning

confidence: 99%

“…Figure 3 shows the results of calculating the parameters χ i × 2 −1 and η in nickel alloys doped with refractory transition metals (Zr, Nb, Mo, Ru, Rh, Hf, Ta, W, Re, and Ir); to study segregation, a special GB ∑5 (210)[100] of the nickel fcc lattice was used [19,23]. The authors [19,23] found that all the considered refractory metals are characterized by negative values of the E gb and η parameters in nickel alloys; that is, they tend to segregate to the GB and increase the cohesive strength of the GB. At the same time, refractory metals increase the cohesion energy of the matrix-a solid solution based on nickel; see Figure 3.…”

Section: Nickel-based Alloysmentioning

confidence: 99%

“…Note the correlation in the behavior of the parameters η and χ when alloying nickel alloys with refractory metals. According to the favorable combination of a high tendency to GB segregation, the effect of strengthening of GB, and the increase in the cohesion energy of the matrix, the authors [19,23] distinguish Zr, Nb, Hf, and Ta among refractory metals, which were recommended for introduction as "low-alloying" additions in nickel HRAs obtained by P/M and having a fine-grained polycrystalline structure.…”

Section: Nickel-based Alloysmentioning

confidence: 99%

“…This approach was used by the authors [19,23,28] to improve the performance characteristics of the Ni-based superalloy EP741NP produced by P/M. To strengthen GBs, the recommended refractory metals (Zr, Nb, Hf, Ta) were introduced into the chemical composition of the EP741NP alloy in small amounts in the form of a package, which made it possible to form a new Ni-based superalloy, NGK6 [29].…”

Section: Nickel-based Alloysmentioning

confidence: 99%

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Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

Razumovskiǐ¹,

Logacheva²,

Razumovskiy

et al. 2021

Metals

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The modern approach to the design of heat-resistant metal alloys (HRAs) is analyzed, according to which the creep rupture characteristics of an alloy are mostly determined by the strength of interatomic bonding at grain boundaries (GBs) and in the bulk of a matrix phase. The main attention is paid to the concept of “low alloying additions” to polycrystalline alloys with transition metals, because of which the cohesive strength of the GBs and the cohesion energy of the alloy matrix are increased. This approach is especially important in relation to alloys obtained by powder metallurgy, which, in the compacted state, are fine-grained polycrystals. The methodology for calculating the key parameters of the theory (the energy of impurity segregation to the grain boundaries Egb and to the free surface Efs, as well as the values of the partial molar energy of the cohesion of the alloys) from the first principles is given. The results of applying the theory to the study of Ni-, Cr- and Ti-based alloys and the development of new HRAs based on them are presented. Typical defects in the microstructures of objects obtained using additive technologies (AT) and the application efficiency of standard methods of processing powder alloys (Hot Isostatic Pressing (HIP), heat treatment (HT)) to improve the microstructure and increase the mechanical properties are considered.

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Section: Titanium-based Alloysmentioning

confidence: 99%

Section: Ti-based Alloysmentioning

confidence: 99%

Section: Nickel-based Alloysmentioning

confidence: 99%

Section: Nickel-based Alloysmentioning

confidence: 99%

Section: Nickel-based Alloysmentioning

confidence: 99%

See 3 more Smart Citations

Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

Razumovskiǐ¹,

Logacheva²,

Razumovskiy

et al. 2021

Metals

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Excellent tensile yield strength with ultrafine grain and tailored microstructure in plastically deformed Ti–Re alloys

Bahador

Amrin

Kariya

et al. 2023

Journal of Alloys and Compounds

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Approaches to the Development of Advanced Alloys Based on Refractory Metals

Razumovskiǐ¹,

Bokstein

Razumovsky

2023

Encyclopedia

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The most promising directions of the development of heat-resistant alloys (HRAs) based on refractory metals are analyzed. The microstructures characteristic of HRAs, which it is advisable to form in promising alloys, are considered. The stability factors of the microstructure with respect to the diffusion coarsening of the hardening phases are discussed. Two groups of alloys are considered as the most promising HRAs based on refractory metals. First, the principles for design of HRAs based on (Pt, Ir)-Sc with heterophase γ-γ’ microstructure, where γ-matrix is a (Pt, Ir) solid solution with a FCC lattice, and γ’ is a strengthening phase with the structure L12 by analogy with Ni-base superalloys, are developed. The resistance of γ-γ’ microstructure in Ni, Pt and Ir alloys against the process of diffusion-limited coarsening is analyzed. It is shown that the diffusion permeability of Pt is several times less than that of Ni, so one should expect that Pt-based HRAs will not be inferior to Ni-based HRAs in terms of structural stability. The second group includes HRAs based on many not noble refractory metals. It is shown that solid solutions of the system (Ti, Zr, Hf, Ta, Nb) with a BCC lattice can be considered as a matrix of advanced refractory HRAs. The results of experimental studies of alloys based on (Ti, Zr, Hf, Ta, Nb) additionally alloyed with elements contributing to the formation of strengthening intermetallic and silicide phases are discussed. The issues of segregation of alloying elements at the grain boundaries of refractory alloys and the effect of segregation on the cohesive strength of the boundaries are considered.

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Segregation of Refractory Metals at Grain Boundaries in High-Temperature Alloys

Cited by 4 publications

References 8 publications

Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

Modern Powder Metallurgy: Chemical Composition Design for Improved Heat Resistant Alloys

Excellent tensile yield strength with ultrafine grain and tailored microstructure in plastically deformed Ti–Re alloys

Approaches to the Development of Advanced Alloys Based on Refractory Metals

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