Evolution of Microstructure, Residual Stress, and Tensile Properties of Additively Manufactured Stainless Steel Under Heat Treatments

This study investigated the microstructure, residual stress, and tensile properties of directed energy deposited stainless steel 316L (SS316L) under thermal annealing. Microstructure characterization shows the as-printed sample has laser-generated patterns where dendritic structure is observed at the edge of the patterns and cellular structure dominates the interior region. The thermal annealing at 983 and 1093 degrees C effectively removes the dendritic/cellular structures. Synchrotron x-ray diffraction reveals that the as-printed SS316L exhibits compressive residual stress of - 197.4 MPa, which is greatly relieved to - 53.8 MPa after annealing at 1093 degrees C. The room temperature tensile testing indicates that the yield strength and ultimate tensile strength drop from 378 MPa and 502 MPa in the as-printed sample to 258 MPa and 446 MPa in the annealed samples (1093 degrees C), respectively. Our study provides insights into the relationship among microstructure, residual stress, and tensile properties of laser additive manufactured SS316L.