This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

Mechanical properties, porosity, and microstructure of Ti6Al4V (ELI) material produced by Selective Laser Melting (SLM) under controlled oxygen content were analyzed. Fully martensitic α’structure with high dislocation density and stacking faults was observed in both as-built and stress relieved samples by means of XRD and TEM. Tensile {101 ̅2} twinning was identified by TEM and electron diffraction. Accommodation of thermal stresses during manufacturing was suggested as a possible reason for twinning. Computed tomography of pores was carried out. Pores in the specimens were evenly distributed and mostly had an elongated shape. Defect analysis by micro CT scans in pre-strained samples confirmed that the pore coalescence was the main crack formation mechanism in the final fracture with typical cup-and-cone fracture morphology. Additionally, typical dimples and quasi-cleavage were revealed. Mechanical properties of the samples after stress relieving heat treatment at 650°C for 3 h are complied with the international standard for Ti alloys for biomedical applications