Investigation of strengthening mechanisms in an additively manufactured Haynes 230 alloy

• Published in: Acta materialia 2022-01, Vol.222, p.117404, Article 117404
• Main Authors: Yang, Bo, Shang, Z., Ding, Jie, Lopez, Jack, Jarosinski, William, Sun, T., Richter, N., Zhang, Y., Wang, H., Zhang, X.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Haynes 230 Ni superalloy; mechanical properties; strengthening mechanism; well-aligned nanoprecipitates
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2021.117404

•The M23C6 carbide precipitates in the as-printed Haynes 230 alloy transformed into M6C carbide and forming well-aligned arrays along direction after stress relief.•The incoherent nanoprecipitates form several types of orientation relationships with the matrix.•In contrast to the conventional dislocation dominated deformation behavior in as-printed alloys, the well-aligned carbide nanoprecipitates in the stress-relieved sample induced nanoscale deformation twins upon tensile deformation, contributing to a greater work hardening ability than the as-printed counterpart. There are abundant studies on additive manufacturing of Ni alloys, such as Inconel 718. However, the studies on the microstructure and the deformation behavior of solid solution strengthened Ni alloys, such as Haynes 230, are limited. Here we compare the microstructure and the mechanical behavior of as-printed and stress-relieved Haynes 230 Ni alloys prepared by laser powder bed fusion. Transmission electron microscopy analysis revealed M23C6 carbides decorated at the dislocation cell walls in the as-printed material transformed to well-aligned arrays of M6C nanoprecipitates separated by an array spacing of 500 nm after stress-relief (heat treatment). The nanoprecipitates in stress-relieved alloy have formed numerous aligned orientation relationships with the matrix despite their large lattice mismatch. Post-tension microscopy analyses demonstrated high-density dislocation networks in the as-printed samples, whereas high-density stacking faults and nanoscale deformation twins were observed in the stress-relieved counterparts. This study provides insights for understanding the influence of nanoprecipitates on the deformation mechanisms of additively manufactured Ni alloys. [Display omitted]