Structure/property (constitutive and dynamic strength/damage) characterization of additively manufactured 316L SS

Abstract

For additive manufacturing (AM), the certification and qualification paradigm needs to evolve as there exists no “ASTM-type” additive manufacturing certified process or AM-material produced specifications. Accordingly, utilization of AM materials to meet engineering applications requires quantification of the constitutive properties of these evolving materials in comparison to conventionally-manufactured metals and alloys. Cylinders of 316L SS were produced using a LENS MR-7 laser additive manufacturing system from Optomec (Albuquerque, NM) equipped with a 1kW Yb-fiber laser. The microstructure of the AM-316L SS is detailed in both the as-built condition and following heat-treatments designed to obtain full recrystallization. The constitutive behavior as a function of strain rate and temperature is presented and compared to that of nominal annealed wrought 316L SS plate. The dynamic damage evolution and failure response of all three materials was probed using flyer-plate impact driven spallation experiments at a peak stress of 4.5 GPa to examine incipient spallation response. The spall strength of AM-produced 316L SS was found to be very similar for the peak shock stress studied to that of annealed wrought or AM-316L SS following recrystallization. The damage evolution as a function of microstructure was characterized using optical metallography.