Necking contributions to σ-phase formation in a hot-corrosion-resistant superalloy during creep exposure

• Published in: Materials characterization 2013-03, Vol.77, p.47-52
• Main Authors: Hou, J.S., Zhou, L.Z., Yuan, C., Guo, J.T., Wang, W., Qin, X.Z., Liaw, P.K.
• Format: Article
• Language: English
• Subjects: Applied sciences; Corrosion; Corrosion environments; Creep; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fractures; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Microstructure; Necking; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solidification; Stress rupture; Superalloy
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2012.11.008

Stress has been shown to accelerate the formation of the σ phase in the experimental Ni-based superalloys during the high-temperature exposure. However, with the necking phenomenon occurring in strained-to-fractured specimens after the creep exposure at 1073K/365MPa for 1700h, the stress decreases, while the amount of the σ phase increases from the fracture face to the end of the fractured gauge section. Nucleation mechanisms of the σ phase are discussed. The energy dynamics analysis indicates that the decrease of the σ-phase density by necking is mainly due to the increased matrix strain energy, while the shape, size, and composition of the σ phase are not affected by necking. ► Necking phenomenon occurs in strained-to-fractured specimens after creep exposure. ► The σ-phase density decreases from fracture face to the end of the gauge section. ► The shape, size, and composition of the σ phase are not affected by necking. ► Stress accelerates the formation of the σ phase during exposure. ► These phenomena are mainly due to the variation of strain energies.