Formation and widening mechanisms of envelope structure and its effect on creep behavior of a multiphase Ni3Al-based intermetallic alloy

Publication date: Available online 14 July 2019Source: Materials Science and Engineering: AAuthor(s): Jing Wu, Chong Li, Yongchang Liu, Xingchuan Xia, Yuting Wu, Yefan Li, Haipeng WangAbstractIn present work, the unique envelope structure (about 1.1 μm in width, and ∼3 vol%) in an as-cast multiphase Ni3Al-based intermetallic alloy was characterized in detail, its formation mechanism during solidification and widening behavior during long-term aging process were analyzed, and relevant effects on creep behaviors of this Ni3Al-based intermetallic alloy under 800 oC/220 MPa were evaluated. Results show that the envelope structure located between the γ'+γ dendrite and interdendritic β phase is γ′-Ni3Al phase with ordered face-centered L12 structure, which plays a vital role in adjoining the heteroid γ'+γ dendrite/interdendritic β phases. The γ′-envelope possesses a coherent orientation relationship of [101]γ'-envelope//[01‾1]dendritic-γ with the dendritic-γ phase (face-centered A1 structure) due to their similar face-centered lattice type, while there exists a semi-coherent transition region between the γ′-envelope (face-centered L12 structure) and interdendritic β phase (body-centered B2 structure) to accommodate their relative lattice mismatching. The formation of γ′-envelope during solidification process is induced by nickel enrichment in the residual liquidoid after interdendritic β phase, and its widening during long-term aging at 800 oC is ma...
Source: Materials Science and Engineering: A - Category: Materials Science Source Type: research