Abstract: Since the conception of three dimensional (3D) printing circa 40 years ago, there has been the proliferation of several additive manufacturing (AM) technologies that enable its use in everyday applications such as aerospace, medicine, military, oil and gas and infrastructure. In order to improve its applicability and growth, 3D printed materials are subjected to the same or even higher levels of scrutiny on its mechanical behavior as their conventionally manufactured counterpart. One of the most important mechanical properties is toughness or the ability of a material to undergo large strain prior to fracture when loaded. In this study, the toughness of 3D printed 15-5 stainless steel was investigated at low (77 K), room (298 K) and high (723 K) temperatures using experimental and numerical modeling of the Charpy impact test. The 15-5 stainless steel specimens were printed (horizontal-build) using the direct metal laser sintering (DMLS) technique, cooled or heated to the specified temperature and tested. The Johnson-Cook (J-C) phenomenological material model and fracture parameters were used in the numerical modeling. The cross-sectional microstructures of surfaces and impact energies of the Charpy impact test were examined. The fracture surface investigation (microsurface analysis as well as visual inspection) and impact energy values of the Charpy impact test show that the 3D printed 15-5 stainless steel exhibited brittle behavior at low and room temperatures, but transitioned into a more ductile behavior at high temperature. At 77 K, 298 K and 723K, the experimental Charpy impact test results were 0.0 J/cm2, 6.78±4.07 J/cm2 and 50.84±3.39 J/cm2 respectively whereas the simulated impact energy were 1.05 J/cm2, 10.46 J/cm2 and 47.07 J/cm2 respectively. Hence, the impact energy for the experimental and numerical simulations were in good agreement; especially at higher temperatures.
Authors: Yi Zhang, Sugrim Sagar, Hye-Young Park, Yeon-Gil Jung, and Jing Zhang
Keywords: 3D printing, additive manufacturing, Charpy impact test, 15-5 stainless steel, microstructure, finite element model, Johnson-Cook model