Micro-layered duplex stainless steel matrix composites with high strength and ductility via laser powder bed fusion

Various complex structures and metallic materials with competitive mechanical properties can be fabricated with the development of laser powder bed fusion (LPBF) technique. However, LPBF-fabricated duplex stainless steels (DSSs) always exhibited high strength but low ductility. To effectively balance the strength and ductility of LPBF-fabricated DSSs, micro-layered DSS matrix composites were obtained by utilizing LPBF and two types of powders: 316L SS powder and the 2507 DSS powder mixed with micron-sized TiC particles. After the alternating deposition of 316L SS powder and the powder mixture, ferrite layers with fine ferrite grains (∼1.5 μm) and austenite layers including bimodal austenite grains (∼2.2 μm; ∼7.3 μm) were found. Fine ferrite grains were found to contain in-situ TiC_xN_y nanoparticles in abundance, and these nanoparticles could also be found in austenite layers. Additionally, two transition areas, including some duplex grains, were produced between the ferrite and austenite layers. In comparison with other reports, the uniform elongation (∼24.3 %) of micro-layered DSS matrix composites was significantly improved while they still exhibited a high strength (ultimate tensile strength: ∼1011 MPa), which was primarily caused by the presence of austenite and ferrite layers, in-situ nanoparticles, and bimodal austenite grains.