Effect of Annealing Temperature and Strain Rate on Mechanical Property of a Selective Laser Melted 316L Stainless Steel

In the present work, 316L stainless steel specimens are fabricated by selective laser melting (SLM) via optimized laser process parameters. The effects of two extrinsic factors, i.e., strain rate and annealing temperature, on the mechanical performance of SLM-processed parts are studied. The two intrinsic factors, namely strain rate sensitivity m and work hardening exponent n, which control the tensile properties of the as-built samples, are quantified. Microstructure characterizations show that cellular structure and crystalline grain exhibit apparently different thermal stability at 873 K. Tensile testing reveals that the yield strength decreases from 584 +/- 16 MPa to 323 +/- 2 MPa, while the elongation to failure increases from (46 +/- 1)% to (65 +/- 2)% when annealing temperature varies from 298 K to 1328 K. The n value increases from 0.13 to 0.33 with the increase in annealing temperature. Due to the presence of fine cellular structures and high relative density achieved in as-printed 316L samples, a strong dependence between tensile yield strength and strain rate is observed. In addition, the strain rate sensitivity of the SLM-produced 316L part (m = 0.017) is much larger than that of conventional coarse-grained part (m = 0.006), whereas the n value increases slightly from 0.097 to 0.14 with increasing strain rate.