Predicting the morphologies of γ' precipitates in cobalt-based superalloys

Journal Article · Wed Sep 06 00:00:00 EDT 2017 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2017.09.003· OSTI ID:1406108

Jokisaari, Andrea M. ^[1]; Naghavi, S. S. ^[2]; Wolverton, C. ^[2]; Voorhees, P. W. ^[2]; Heinonen, O. G. ^[3]

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1. Northwestern Univ., Evanston, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)
2. Northwestern Univ., Evanston, IL (United States)
3. Northwestern-Argonne Institute of Science and Engineering, Evanston, IL (United States); Argonne National Lab. (ANL), Lemont, IL (United States)

Cobalt-based alloys with γ/γ' microstructures have the potential to become the next generation of superalloys, but alloy compositions and processing steps must be optimized to improve coarsening, creep, and rafting behavior. While these behaviors are different than in nickel-based superalloys, alloy development can be accelerated by understanding the thermodynamic factors influencing microstructure evolution. In this work, we develop a phase field model informed by first-principles density functional theory and experimental data to predict the equilibrium shapes of Co-Al-W γ' precipitates. Three-dimensional simulations of single and multiple precipitates are performed to understand the effect of elastic and interfacial energy on coarsened and rafted microstructures; the elastic energy is dependent on the elastic stiffnesses, misfit strain, precipitate size, applied stress, and precipitate spatial distribution. We observe characteristic microstructures dependent on the type of applied stress that have the same γ' morphology and orientation seen in experiments, indicating that the elastic stresses arising from coherent γ/γ' interfaces are important for morphological evolution during creep. Here, the results also indicate that the narrow γ channels between γ' precipitates are energetically favored, and provide an explanation for the experimentally observed directional coarsening that occurs without any applied stress.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: National Institute of Standards and Technology (NIST), Center for Hierarchical Materials Design (CHiMaD); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22), Scientific User Facilities Division; USDOE Office of Science (SC), National Energy Research Scientific Computing Center (NERSC)
• Grant/Contract Number: AC02-05CH11231; AC02-06CH11357
• OSTI ID: 1406108
• Alternate ID(s): OSTI ID: 1549940
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: C Vol. 141; ISSN 1359-6454
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Coarsening
Cobalt-base superalloys
Phase field model
Rafting