Effects of annealing temperature on cellular structure and mechanical properties of additively manufactured 304L stainless steel by directed energy deposition
J. S. Kim, Y.B. Chun, Suk Hoon Kang, Bong Sang Lee
Abstract
The mechanical properties of additively manufactured 304L stainless steel are strongly influenced by cellular structures, which include high dislocation densities, low-angle grain boundaries, and elemental segregation. To investigate the impact of these features on material strength, the as-built 304L stainless steel was subjected to annealing treatments at temperatures ranging from 750°C to 1150°C. The microstructural changes within the cellular structures after annealing were analyzed using electron microscopy techniques. The contributions of each microstructural feature to the yield strength were quantitatively assessed and compared with the yield strengths obtained from tensile testing. It demonstrates that elemental segregation and dislocation density on the cellular structures are the dominant factors governing the high yield strength of additively manufactured 304L stainless steel. In addition, it was confirmed that elemental segregation in the cellular structure can affect the martensitic transformation under tensile deformation, which may affect the strain induced plasticity (TRIP) effect. • Additively manufactured 304L stainless steel produced using directed energy deposition exhibits a hierarchical microstructure at low-angle grain boundaries and solidification cell boundaries with different element segregation. • The changes in the hierarchical microstructure were investigated after annealing at various temperatures (750°C-1150°C). • Strengthening models were applied to quantitatively assess the contributions of each microstructural component to yield strength. • Element segregation and dislocation density were identified as primary factors contributing to the high yield strength of additively manufactured 304L stainless steel.