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Effects of additive heat source type and heat treatment on microstructural evolution and mechanical properties of Inconel 718 alloy fabricated by directed energy deposition
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DOI：10.1016/j.matchar.2026.116422.png)
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Abstract
En 中文
This study systematically compares the thermal cycling histories, microstructural evolution, precipitation behavior, and mechanical properties of thin-walled Inconel 718 (IN718) alloy structures fabricated by wire-arc directed energy deposition (DED) and wire-laser DED. The results demonstrate that wire-laser DED, owing to its substantially higher cooling rate, effectively suppresses interdendritic Nb segregation and the coarsening of the Laves phase, reducing the Laves phase area fraction in the as-deposited state to 6.99%, which is 18.3% lower than that obtained by wire-arc DED. Meanwhile, significant grain refinement is achieved, with the fraction of HAGBs increasing to 89.4%, markedly higher than the 65.8% observed for wire-arc DED, resulting in increases of 15.0% and 17.8% in the tensile strength of the as-deposited samples along the horizontal (H) and vertical (V) directions, respectively. After heat treatment, the wire-laser DED samples benefit from their finer initial grain size, which shortens elemental diffusion paths, promotes the uniform precipitation of gamma' and gamma '' phases with higher volume fractions, and leads to a stronger dislocation pinning effect. Consequently, the heat-treated wire-laser DED samples achieve tensile strengths of 1216.2 MPa and 1275.5 MPa in the H and V directions, respectively, approaching those of wrought counterparts and significantly exceeding those of the heat-treated wire-arc DED samples. Compared with the as-deposited condition, the tensile strength of the wire-laser DED samples after heat treatment increases by 47.7% and 48.5% in the H and V directions, respectively. This study systematically clarifies how variations in heat source type affect microstructural evolution and mechanical performance in additively manufactured IN718 alloy, providing a theoretical framework and practical guidance for process optimization and engineering applications.
Keywords:
IN718 alloy
Microstructural evolution
Mechanical properties
Heat treatment
Precipitation strengthening
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