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This article presents an investigation of grain boundary serration and its effects on high temperature creep behavior of Udimet-720Li. Grain boundary serration is achieved by controlling the cooling conditions during heat treatments through continuous and discontinuous precipitation of γ′. Continuous precipitation of coarse γ′ particles could pin grain boundaries and lead to a small degree of undulation (Type-I boundary), while discontinuous reaction forming cellular γ/γ′ behind the mobile grain boundary could cause larger undulation (Type-II boundary). Samples with straight (STB), Type-I (SRB-1), Type-II (SRB-2) grain boundaries were produced. Creep tests under 700 °C / 700 MPa have been conducted to investigate its effect on creep behaviors. It was observed that the SRB-1 sample exhibited a notably lower minimum creep rate and longer rupture lifetime than that of the STB sample. These improvements are primarily attributed to the different size distribution of γ′ precipitates, which contributes to a higher hindrance to dislocation movements. Conversely, the SRB-2 sample exhibited a higher minimum creep rate, and a considerable 42% reduction in rupture lifetime in contrast to the STB sample. This is mainly due to the enhanced grain boundary fractions due to the formation of Type-II serration in the SRB-2 sample, promoting grain boundary diffusion creep.

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• In Copyright
  

Keyword: Superalloys, Heat treatment, Serrated grain boundary, Creep properties

Date published: 2024-08-21

Publisher: Springer Nature Switzerland

Journal:

• Minerals, Metals and Materials Series (ISSN: 23671181) vol. 1 p. 297-305

Funding:

• National Science and Technology Council (NSTC) in Taiwan NSTC 112-2927-I-007-504
• National Science and Technology Council (NSTC) in Taiwan NSTC 110-2221-E-007-020- MY3
• NSTC 112-2224-E-007-003 (National Science and Technology Council (NSTC) in Taiwan)
• Ministry of Education (MOE) in Taiwan (The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project)

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4851

First published URL: https://doi.org/10.1007/978-3-031-63937-1_28

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Updated at: 2025-08-21 08:30:42 +0900

Published on MDR: 2025-08-21 08:19:15 +0900