With the rapid development of additive manufacturing technology, selective laser melting (SLM) of austenitic stainless steel has been widely used. SLM stainless steel will inevitably deform during service, so it is necessary to study the microstructure and macro properties of post-plastic deformed SLM stainless steel. In this paper, the changes in the microstructure, mechanical properties, and corrosion resistance of SLM304 stainless steel after stretch deformation were studied, and the evolution rules were revealed. The results show that, with an increasing plastic deformation amount, SLM304 stainless steel exhibits grain fragmentation, disordered orientation, and subgrain formation, along with changes in the shape and size of the cellular structure. Additionally, the α’ martensite content inside SLM304 stainless steel rises significantly, while the thickness of the surface passivation film slightly decreases. The analysis shows that the combined effect of the complex microstructure makes the nanohardness of SLM304 stainless steel increase with the increase in the stretch deformation amount while its corrosion resistance deteriorates. Therefore, moderate post-plastic deformation can enable SLM stainless steel to balance excellent mechanical and corrosion properties. This study can not only provide a theoretical reference for the performance optimization of additive manufacturing steel but also provide value for the engineering application of additive manufacturing technology.

This paper investigates the evolution of the microstructure, mechanical performances, and corrosion resistance of selective laser melting (SLM) 304 steel under different intermittent stretching deformation step sizes, revealing the underlying evolution patterns. The results indicate that the intermittent deformation step size significantly affects the microstructure and performance of SLM 304 steel. Larger step sizes result in more complete molten pool contours, less deformation of grain and cellular structures, and a lower martensite volume fraction; smaller step sizes lead to distorted molten pools, fragmented grains, exacerbated cellular structure distortion, and increased martensite content. In terms of mechanical performances, tensile strength, nano-hardness, and elastic modulus decrease with increasing step size, while elongation increases accordingly. Corrosion resistance improves with larger step sizes, with specimens exhibiting more complete and thicker oxide films on the surface and superior pitting resistance; continuous stretching specimens exhibit the worst corrosion resistance, while the original specimens are the best. Intermittent deformation optimizes properties by regulating microstructure, providing a basis for the design of high-performance SLM 304 steel. This study provides theoretical support for the design and application of additive manufacturing stainless steel components, facilitating the engineering and industrial application of SLM technology in high-end equipment manufacturing.