Abstract
The evolution of oxygen-rich nanoparticles in selective laser melted 304L stainless steel (SLM 304L SS) and its effect on the mechanical property were studied by adjusting the heat treatment process. The nanoparticles mainly contained oxygen, chromium, and silicon; the average size of oxygen-rich nanoparticles increased with the temperature of heat treatment. The nanoparticles were Cr-rich phases when treated below 950 °C, while the nanoparticles were Si-rich oxides when treated at 1100 °C. With the increase in the temperature of heat treatment, the molten pool boundaries and cellular structures of SLM 304L SS gradually disappeared and the yield strength decreased obviously. The boundary of the cellular structure with high dislocation density provides a fast channel for atom diffusion, and thus it becomes the preferred nucleation site for nanoparticles. The dispersed nanoparticles are not only the strengthening phases but also can hinder the movement of dislocations, and thus they can greatly improve the strength of the material without sacrificing ductility.
Published Version
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