Direct energy deposition of high strength austenitic stainless steel matrix nanocomposite with superior ductility: Microstructure, tensile properties, and deformation behavior

• Published in: Materials characterization Vol. 179; p. 111358
• Main Authors: Kim, Young-Kyun, Lee, Kee-Ahn
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2021
• Subjects: Deformation behavior; Direct energy deposition; Microstructure; Stainless steel matrix nanocomposite; Tensile; Stainless steel matrix nanocomposite; Tensile; Microstructure; Deformation behavior; Direct energy deposition
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2021.111358

Direct energy deposition (DED) was used to additively manufacture 22–13-5 austenitic stainless steel (SS), of which the mechanical properties and corrosion resistance are superior to those of SS316L and SS304L. Additionally, in-situ formed oxide-driven strengthening was utilized in this study. The DED-processed austenitic SS matrix nanocomposite (SSMNC) exhibited unique microstructural features of heterogeneous grains and dislocation networks. The nano-sized precipitates existed at the sub-structure boundaries and decorated the dislocation network. The results of the transmission electron microscopy (TEM)-energy loss spectroscopy (EELS) analyses revealed nano-sized precipitates with an average size of 21.1 nm that were identified as (Mn,Cr)-rich oxides. This means that, during the DED process, the oxygen in the powder feedstock transformed into nano-sized oxide particles by rapid solidification. The DED-processed SSMNC revealed a yield strength of 705.4±5.3 MPa, which is higher than those of reported AM-processed stainless steels. In addition, the elongation-to-failure was measured as 41.8±3.5%. This suggests that the DED-processed SSMNC has an excellent combination of strength and ductility at room temperature. The high ductility of the alloy developed in this work was found to be achieved by a twinning-induced plasticity (TWIP) mechanism that operated during the deformation. Based on the above findings, the relationships between the microstructure, mechanical properties, and deformation mechanism are also discussed. •22–13-5 austenitic stainless steel matrix nanocomposite (SSMNC) was successfully manufactured by direct energy deposition.•DED-processed SSMNC shows heterogenous grain, dislocation networks and in-situ nano-sized (Mn,Cr)-rich oxide.•DED-processed SSMNC reveals ultra-high strength with excellent ductility.