Selective laser melting (SLM) is a transformative additive manufacturing technique that enables the production of complex metallic components with high precision. Understanding the microstructural evolution during the SLM process is crucial for optimising the mechanical properties and performance of the fabricated parts. This study focuses on developing a predictive model for the microstructure evolution of Ti6Al4V alloy during SLM. The model integrates thermal simulations with phase transformation kinetics using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory to predict the formation and dissolution of alpha and martensite phases. The thermal history of the SLM process was simulated using Finite Element Analysis (FEA) in Abaqus, which provided the temperature distribution and cooling rates experienced by the material. These thermal profiles were then used to drive the microstructure evolution model, which predicts the phase fractions and grain structures resulting from the SLM process. The model was validated against experimental data, showing good agreement in predicting phase fractions and microstructural features. Our results highlight the significant impact of processing parameters, such as laser power and scanning speed, on the microstructure of Ti6Al4V. Higher laser powers and slower scanning speeds were found to promote the formation of coarser microstructures, while faster cooling rates led to finer grains and higher martensite fractions. This comprehensive modelling approach provides valuable insights into optimising SLM process parameters to achieve desired microstructural characteristics and improve the mechanical performance of Ti6Al4V parts. The developed model is a robust tool for guiding the design and optimisation of SLM processes, reducing the reliance on trial-and-error methods, and enhancing the efficiency and quality of additive manufacturing for critical applications in aerospace, biomedical, and automotive industries.

Selective laser melting (SLM) is an additive manufacturing technique in which a laser beam with a high energy density is used to melt a metal powder substrate. Although this technique has several advantages, including the possibility of fabricating complex metal components quickly, there are concerns about the mechanical properties of the parts produced by the SLM method. This is study aims to ensure the achievement of acceptable mechanical properties including yield stress, tensile strength, and elongation percentage compared to conventional manufacturing methods. For this purpose, samples of 316L stainless steel were printed using the SLM machine. These samples and samples of annealed 316L bar were tested under same conditions and by the same equipment. Despite the large differences in microscopic structure, no significant differences were observed in mechanical properties. Also, the obtained results were compared with the results related to the sample made by the DLD additive manufacturing method, which is similar to SLM in terms of energy source and raw materials. The result represents that the mechanical strength and microhardness of the sample produced by the SLM technique are higher than the other samples, and the elongation percentage is within the desirable range. The yield stress, tensile strength, and elongation are respectively 595Mpa, 696Mpa, and 34. 5%, all of which are within the acceptable range required by the standards for such samples. The investigation of the microstructure shows a complete austenitic cellular structure without considerable solidification defects. Overall, the SLM additive manufacturing is a reliable process to produce 316L stainless steel parts in terms of mechanical properties.

In the present work, the Selective laser melting (SLM) has been chosen as a controlled thermomechanical processing route in which the required temperature and strain for the occurrence of dynamic recrystallization is provided. The 316L stainless steel as representative material was constructed by SLM under specified parameters (laser power, layer thickness, hatch spacing, scan strategy, and scan speed). The printed material’, s microstructure was carefully analyzed through electron back scattered diffraction. The presence of considerable fine grains (< 20 μ, m) through the printed microstructure was considered as evidence for the occurrence of dynamic recrystallization during the manufacturing process. The high fraction of sub-boundaries (~79. 7%) and sub-grains indicated the capability of the material for substructure development in the course of additive manufacturing process, and the fact that the new fine grains were formed through continuous dynamic recrystallization mechanism. The creation of plastic strains through the parts structure during SLM, which was required for dynamic recrystallization, was discussed relying on the expansion and contraction of the layers during repeated heating and cooling cycles. The amount of plastic microstrain was estimated to be around ~0. 56 considering the layer thickness and depth of the melt pool. The hot compression tests were conducted at 1000℃,and various strain rates of 0. 001, 0. 01 and 0. 1 s-1 and the corresponding critical strains of dynamic recrystallization (~0. 2) were calculated, which was well lower than those created during additive manufacturing process.