Deformation modes and yield strength anomaly in L12 compounds

Vamsi, K.V.

doi:10.1016/j.jallcom.2020.158411

Cited by 15 publications

(1 citation statement)

References 53 publications

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“…Most fault energies of multicomponent compositions calculated with this approach were negative. Previous work by Vamsi (143) shows that PFEs for pseudobinary compositions can be modeled by an environment-dependent nearest-neighbor bond model, in which fault energies have a cubic dependence on composition. This model explains why a simple linear averaging scheme fails to predict PFEs for complex compositions.…”

Section: Alloying Effects In Ni- Co- and Coni-base Superalloysmentioning

confidence: 99%

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

Eggeler

Vamsi

Pollock

2021

Annu. Rev. Mater. Res.

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The mechanical properties of superalloys are strongly governed by the resistance to shearing of ordered precipitates by dislocations. In the operating environments of superalloys, the stresses and temperatures present during thermomechanical loading influence the dislocation shearing dynamics, which involve diffusion and segregation processes that result in a diverse array of planar defects in the ordered L12 γ′ precipitate phase. This review discusses the current understanding of high-temperature deformation mechanisms of γ′ precipitates in two-phase Ni-, Co-, and CoNi-base superalloys. The sensitivity of planar fault energies to chemical composition results in a variety of unique deformation mechanisms, and methods to determine fault energies are therefore reviewed. The degree of chemical segregation in the vicinity of planar defects reveals an apparent phase transformation within the parent γ′ phase. The kinetics of segregation to linear and planar defects play a significant role in high-temperature properties. Understanding and controlling fault energies and the associated dislocation dynamics provide a new pathway for the design of superalloys with exceptional properties.

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Section: Alloying Effects In Ni- Co- and Coni-base Superalloysmentioning

confidence: 99%

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

Eggeler

Vamsi

Pollock

2021

Annu. Rev. Mater. Res.

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Platinum Years of Metallurgical and Materials Education and Research—The IISc Saga

Subramanian,

Suwas,

Ranjan

et al. 2023

Indian Institute of Metals Series

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Stability and Physical Properties of the L12-γ′ Phase in the CoNiAlTi-System

Pyczak

Liang

Neumeier

et al. 2023

Metall Mater Trans A

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There is a current interest in Co-based superalloys hardened by a L12-γ′ phase because Co has a higher melting point than Ni and is more resistant against sulfidation attack. However, the Co-Al-W system many of those γ′ hardened Co-based superalloys are based on, has a number of drawbacks. The γ′ phase Co3(Al,W) is not stable at high temperature, the density of the alloys is very high and the oxidation resistance is insufficient. Due to this, there is an ongoing interest to develop γ′-hardened Co-based superalloys based on other systems. Here, first principles calculations are presented to investigate the properties of the γ′ L12-(Co0.5,Ni0.5)3(Al0.5,Ti0.5) phase and related L12 structures. (Co0.5,Ni0.5)3(Al0.5,Ti0.5) exhibits a lower energy of formation than Co3Ti and Co3(Al0.5,W0.5). Nevertheless, Ni3(Al0.5,Ti0.5) has an even lower energy of formation which is further lowered if Ti is enriched on the second sublattice. This finding is supported by analyzing the electronic densities of states. Ni3(Al0.5,Ti0.5) and especially Ni3(Al0.25,Ti0.75) exhibit Fermi levels close to the gap between binding and antibinding states, which is an indicator for stability. In addition to the stability of the γ′-phase in dependence on Ni and Ti content, also the elastic properties were calculated. Ni3(Al0.25,Ti0.75) is less elastic anisotropic and has higher Young’s and shear modulus compared to Ni3(Al0.5,Ti0.5) and (Co0.5,Ni0.5)3(Al0.5,Ti0.5).

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Deformation modes and yield strength anomaly in L12 compounds

Cited by 15 publications

References 53 publications

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

Precipitate Shearing, Fault Energies, and Solute Segregation to Planar Faults in Ni-, CoNi-, and Co-Base Superalloys

Platinum Years of Metallurgical and Materials Education and Research—The IISc Saga

Stability and Physical Properties of the L12-γ′ Phase in the CoNiAlTi-System

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