In Situ x-ray Diffraction Study of the Deformation of an AISI 316L Stainless Steel Produced by Laser Powder Bed Fusion

• Published in: Journal of materials engineering and performance Vol. 31; no. 10; pp. 8013 - 8026
• Main Authors: Starck, Leticia F., Zilnyk, Kahl D., Senra, Ana L. T., Namur, Ricardo S., Izumi, Marcel T., de Castro, Maurício, Maeda, Milene Y., Righetti, Victor A. N., Ramirez, Antonio J., Cintho, Osvaldo M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-10-2022
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion and Coatings; Engineering Design; Materials Science; Quality Control; Reliability; Safety and Risk; Technical Article; Tribology; in situ x-ray diffraction; additive manufacturing; heat treatment; laser powder bed fusion; 316-L austenitic stainless steel
• DOI: 10.1007/s11665-022-06851-z
• EISSN: 1544-1024
• ISSN: 1059-9495

Additive manufacturing (AM) has emerged as an outstanding technique for obtaining complex geometries and custom parts, without the material loss of conventional subtractive manufacturing processes. In this work, AISI 316L stainless steel specimens were fabricated by laser powder bed fusion (L-PBF), and its microstructure was characterized by several techniques. Tensile tests with in situ x-ray diffraction (XRD) measurements were performed using synchrotron radiation. Stress–strain curves and diffractograms were obtained for the as-printed AM 316L, annealed AM 316L and conventional/rolled 316L samples for comparison. The results indicated lower ductility for the AM samples when compared to the sheet. This can be a result of the remaining porosity associated with the AM process. The annealing of the AM samples led to a reduction of the residual stress and an improvement of ductility without significant loss on the ultimate tensile strength. In situ XRD data indicated that AM samples did not undergo phase transformation during straining, maintaining a fully austenitic microstructure and preventing a transformation-induced plasticity (TRIP) effect. On the other hand, in the rolled sample, peaks of α′-martensite were identified. Electron backscattered diffraction (EBSD) measurements indicated that a random texture was achieved by the parameters and scanning strategy used. The results indicate that process parameters must be carefully chosen in order to avoid porosity, and excessive residual stresses, features that directly affect the mechanical behavior of the material.