Atomistic Study on the Cooling Rate Induced Mechanical Properties Variations in Additively Manufactured Inconel-718

Abstract

Abstract Inconel 718 is a highly sought-after material for use in additive manufacturing, which is also known as 3D printing. Additive manufacturing is a process of building three-dimensional objects by layering materials on top of one another, based on a computer-generated design. Inconel 718 is very popular in additive manufacturing because of its unique properties, including high strength, high-temperature resistance, and excellent corrosion and oxidation resistance. This paper uses atomistic tensile test simulation to investigate the mechanical properties of additively manufactured Inconel 718. The study explores the effects of different cooling rates on Inconel-718 material using the large-scale atomic/molecular massively parallel simulator (LAMMPS). Throughout this study, the added layers on a pristine substrate have been equilibrated at 2000K and subsequently cooled to 300K using a cooling rate ranging from 5 K/ps to 100 K/ps including a variable cooling rate. Embedded atom method (EAM) potential has been used to investigate the dislocations, voids, defects, and atomic interactions, which control the material properties and failure mechanisms. A nano bar of (22nm × 5.5 nm × 5.5 nm) has been cut from the solidified layer for tensile test. The tensile force has been applied along [001] direction. The strain rate has been varied from 108 s−1 to 1010 s−1. Tensile test simulation shows that the additively manufactured Inconel 718 has a lower yield strength and elongation than the conventionally manufactured material but exhibits comparable ultimate tensile strength. The results show that the variation of cooling rate significantly impacts the mechanical properties, demonstrating that increasing the cooling rate causes the final material to have a lower density, higher number of defects, and lower Young’s modulus. In contrast, lower cooling rates cause the final structure to exhibit properties similar to its pristine counterpart. These MD simulations provide insights into the deformation behavior, ultimate tensile strength, Young’s Modulus, fracture strain, and dislocation density at the atomic level and suggest that the observed differences in mechanical properties can be attributed to the presence of defects and microstructural features induced by different cooling rates of the additive manufacturing process. The fracture evolution at different cooling rates has also been analyzed. Results from this computational study also show that extensive sliding in {111} shear plane that again depends on the cooling rate causes necking before fracture. Overall, the findings highlight the importance of careful process control in additive manufacturing and demonstrate the potential of MD simulations for predicting the mechanical behavior of such materials.