Anisotropic tensile behavior of in situ precipitation strengthened Inconel 718 fabricated by additive manufacturing

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 701; pp. 344 - 351
• Main Authors: Ni, Mang, Chen, Chao, Wang, Xiaojun, Wang, Pengwei, Li, Ruidi, Zhang, Xiaoyong, Zhou, Kechao
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 31.07.2017; Elsevier BV
• Subjects: Additive manufacturing; Anisotropy; Coloumnar grain; Cooling rate; Damage accumulation; Elongation; Grain boundaries; IN718; Laser beam melting; Laser cooling; Laser processing; Mechanical properties; Microstructure; Nickel base alloys; Precipitates; Selective laser melting; SLM; Superalloys; Tensile strength; Texture; Ultimate tensile strength; Coloumnar grain; IN718; Selective laser melting; Anisotropy; SLM
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2017.06.098

This study investigated the microstructure and anisotropic mechanical properties of selective laser melting (SLM) processed Inconel 718 (IN718) component. In as-fabricated alloys, ultrafine columnar grained microstructure with highly dispersed precipitates γ" phases at grains boundary and even-distributed γ' phases inside the grains were observed. It was demonstrated that the as-fabricated longitudinal samples showed lower ultimate tensile strength (UTS) of 1101MPa but higher elongation of 24.5% compared to the transverse samples which showed UTS of 1167MPa and elongation of 21.5%. The excellent mechanical properties of both the longitudinal and transverse samples can be ascribed to the refined microstructure of the SLM material resulting from the high cooling rate imposed by laser processing. The anisotropy in strength and ductility was attributed to the {100} fiber texture and columnar grain morphology. The {100} fiber texture of columnar grains leads to high strength in transverse direction, while the columnar grain boundaries also served as a path along which damage can preferentially accumulate, leading to fracture.