Title of Paper:Grain boundary migration-induced directional coarsening of the gamma ' phase in advanced ultra-supercritical superalloy

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Date of Publication:2018-01-31

Journal:MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

Included Journals:SCIE、EI

Volume:714

Page Number:172-178

ISSN No.:0921-5093

Key Words:Creep; Ni-based superalloy; Advance ultra-supercritical; Microstructure; Grain boundary

Abstract:This study investigated the features of grain boundary regions in a Ni-based superalloy which underwent creep deformation. Large grain boundary zones were denuded in fine gamma' precipitates but contained coarsened micro scale gamma' rods. The coarsening direction of these rods was along the < 110 > of the gamma matrix and gamma' precipitates. The orientation of the grain boundary zone was the same as that of the adjacent grain behind the migrating boundary. This result indicated that the formation of these zones was accompanied by the migration of the grain boundary. Then, numerous slip features were observed through detailed local disorientation analysis. It is proposed that the driving force for the grain boundary migration was the local stress induced by the dislocation creep. The dissolution reprecipitation of the precipitates at the boundary migration front resulted in the directional coarsening of the gamma' rods.