Mechanical properties of SLM 316L stainless steel plate before and after exposure to elevated temperature

Selective Laser Melting (SLM) additive manufacturing (AM) is recognized for its rapid production capabilities, energy efficiency, reduced environmental impact, and design flexibility. It has shown promising applications in architecture and civil infrastructure. However, before applying this technology to the actual production of building structures, it is necessary to develop corresponding constitutive models to predict the material behaviour accurately. Previous studies on the mechanical properties of SLM 316 L stainless steel (SS) have not been comprehensive enough, particularly regarding the mechanical properties after exposure to elevated temperatures. This paper explores the effects of build orientation (X, Y, and Z construction orientations), layer thickness (2 mm, 4 mm and 6 mm), and thermal treatment (20°C, 300 °C, 600 °C, and 900 °C) on the mechanical properties of SLM-produced 316 L SS plates. Monotonic tensile tests and scanning electron microscopy (SEM) are employed to evaluate the mechanical characteristics and microstructure of the plates. Results indicate that the mechanical properties vary with manufacturing direction and material thickness. Specifically, properties are enhanced in the X and Y directions compared to the Z direction, and generally decline with increased material thickness except for elongation at fracture. Elevated temperature treatment has a significant effect on the mechanical properties of SLM 316 L SS. Thermal treatments at temperatures below 600 °C are found to increase yield and ultimate tensile strengths, whereas exposures at 900 °C decrease strength but increase ductility. The elastic modulus remains relatively unaffected by temperature changes. A reduction model is developed to assess the mechanical properties of SLM 316 L SS, introducing a new coefficient that predicts the variation in the elastic modulus, yield strength, ultimate tensile strength, elongation, strain hardening parameters, and Poisson's ratio before and after thermal exposure. This model has been calibrated to effectively represent the mechanical properties of SLM 316 L SS under different manufacturing conditions and provides a foundation for future research on other alloy systems and heat treatment protocols.