The microstructural evolution and mechanical response of laser direct energy deposition Inconel 718 alloy based on simulation and experimental methods

Abstract

During laser directed energy deposition (LDED), the complex microstructure created by multiple rapid heating and cooling cycles results in the uneven performance of the parts. This work investigates the microstructure evolution and mechanical properties of LDED Inconel 718 samples with different deposit shapes of single-track and thin-wall. The crystal plasticity constitutive and statistical microstructure modeling combined with experiments were performed to explore the influence of microstructure on tensile property. Compared to the thin-wall samples, the single-track sample has smaller sub-grains because of the higher cooling rate, resulting in higher hardness. Furthermore, the anisotropy of the mechanical properties is not changed by the scanning strategy, although the grain size and the yield strength with the Hall-Petch relation are affected by the scanning strategy. The slip system with maximum and secondary Schmid factors is more easily activated during deformation. The rotational behavior of the grains suggests that the anisotropy of mechanical properties is closely linked to the dominant texture of the 〈001〉 orientation crystals, including the dominant direction of the grain long axis and the ratio of the long and short axis. The results can provide guidance for understanding the deformation mechanism of LDED parts and optimizing the strength design.