Effect of Ti2AlC Addition on the Microstructure and Mechanical Property of Additive Manufactured Inconel 718 Alloys via Laser Powder Bed Fusion

Abstract

Improving the high-temperature performance of Inconel 718 (IN718) alloys manufactured via laser powder bed fusion (LPBF) has been the most concerned issue in the industry. In this study, the effects of Ti₂AlC inoculants on microstructures and high-temperature mechanical properties of the as-built IN718 composites were investigated. According to statistical results of relative density and unmelted particle area in as-built alloys, the optimal energy of 112 J/mm³ was determined. It was observed that the precipitation of the MC carbide was significantly enhanced with the addition of Ti₂AlC, restricting the precipitation of the Laves phase. The MC particles were uniformly distributed along the subgrain boundaries, which contributed to the dispersion strengthening. Meanwhile, the MC particles served as nucleation sites for heterogeneous nucleation during the solidification process, facilitating the refinement of columnar and cellular grains. The simulated Scheil–Gulliver curves showed that the precipitation sequence of phases did not change with Ti₂AlC inoculants. The as-built 1%Ti₂AlC/IN718 sample demonstrated an ultimate tensile strength of 998.78 MPa and an elongation of 18.04% at 650 °C, revealing a markedly improved mechanical performance compared with the LPBF-manufactured IN718 alloys. The high-temperature tensile strength of 1%Ti₂AlC/IN718 sample increased to 1197.99 MPa by heat treatment. It was suggested that dislocation strengthening and ordered strengthening were two most important reinforcement mechanisms.