Mechanical Response of Additively Manufactured Stainless Steel 304L Across a Wide Range of Loading Conditions

Technical Report · Sat Jun 01 04:00:00 EDT 2019

DOI:https://doi.org/10.2172/1762664· OSTI ID:1762664

Adams, David P. ^[1]; Reedlunn, Benjamin ^[1]; Maguire, Michael Christopher ^[2]; Song, Bo ^[1]; Carroll, Jay ^[1]; Bishop, Joseph E. ^[1]; Wise, Jack L. ^[1]; Kilgo, Alice ^[1]; Palmer, Todd A. ^[3]; Brown, Don W. ^[4]; Clausen, Bjorn ^[4]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
3. Pennsylvania State Univ., University Park, PA (United States)
4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The mechanical response of additively manufactured (AM) stainless steel 304L has been investigated across a broad range of loading conditions, covering 11 decades of strain rate, and compared with the behaviors of traditional ingot-derived (wrought) material. In general, the AM material exhibits a greater strength and reduced ductility compared with the baseline wrought form. These differences are consistently found from quasi-static and high strain rate tests. A detailed investigation of the microstructure, the defect structure, the phase, and the composition of both forms reveals differences that may contribute to the differing mechanical behaviors. Compared with the baseline wrought material, dense AM stainless steel 304L has a more complex grain structure with substantial sub-structure, a fine dispersion of ferrite, increased dislocation density, oxide dispersions and larger amounts of nitrogen. In-situ neutron diffraction studies conducted during quasi-static loading suggest that the increased strength of AM material is due to its initially greater dislocation density. The flow strength of both forms is correlated with dislocation density through a square root dependence akin to a Taylor-like relationship. Neutron diffraction measurements of lattice strains also correlate with a crystal plasticity finite element simulations of the tensile test. Other simulations predict a significant degree of elastic and plastic anisotropy due to crystallographic texture. Hopkinson tests at higher strain rates $$\dot{ε}$$ = 500 and 2500 s^-1 ) also show a greater strength for AM stainless steel 304L; although, the differences compared with wrought are reduced at higher strain rates. Gas gun impact tests, including reverse ballistic, forward ballistic and spall tests, consistently reveal a larger dynamic strength in the AM material. The Hugoniot Elastic Limit (HEL) of AM SS 304L exceeds that of wrought material although considerable variability is observed with the AM material. Forward ballistic testing demonstrates spall strengths of AM material (3.27 -- 3.91 GPa) that exceed that of the wrought material (2.63 -- 2.88 GPa). The Hugoniot equation-of-state for AM samples matches archived data for this metal alloy.

• Research Organization: Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Pennsylvania State Univ., University Park, PA (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA); USDOE Laboratory Directed Research and Development (LDRD) Program
• DOE Contract Number: AC04-94AL85000; NA0003525
• OSTI ID: 1762664
• Report Number(s): SAND--2019-7001; 676638
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE