Enhanced mechanical characteristics of Inconel-718 lattice structures produced by laser powder-based fusion with heat treatments

Abstract

This thesis explores the mechanical properties of four lattice structures—BCC, diamond, IWP, and gyroid—selected for their load-carrying and energy absorption capabilities. Compression tests reveal that the BCC and diamond structures exhibit larger plastic zones, while the IWP demonstrates superior energy absorption per volume, attributed to its smoother surface geometry resembling the BCC structure. The gyroid structure displays the highest yield strength. The selected heat treatments, HT1, HT2, and HT3, yield similar results, though variations in microstructure and grain size significantly affect mechanical properties. HT2, with its δ-phase boundaries, exhibits promising outcomes. The combination of HT2 and gyroid structure enhances yield strength by 94%, making it ideal for high-strength applications. Similarly, the pairing of IWP and HT2 increases energy absorption per volume by 48%, suitable for energy dissipation applications. XRD analysis revealed significant changes in the principal crystalline planes (111, 200, and 220) across different heat treatments. HT2 exhibited the most pronounced phase transformations, with sharp XRD peaks and reduced microstrain, correlating with the largest grain sizes and the highest mechanical performance. HT1 showed initial microstructural adjustments with smaller grain growth and moderate mechanical properties, while HT3 resulted in a balanced microstructure with stable and moderate mechanical performance. Integrating lattice structures with heat treatments enhances material properties, with HT2 emerging as a promising treatment for advanced material applications. Recommendations for future research include exploring microstructural evolution, long-term material performance, fatigue behavior, and cooling rate effects.