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Solid-State Transformation of an Additive Manufactured Inconel 625 Alloy at 700 °C



Fan Zhang, Jan Ilavsky, Greta Lindwall, Mark R. Stoudt, Lyle E. Levine, Andrew J. Allen


Inconel 625, a nickel-based superalloy, has drawn much attention in the emerging field of additive manufacturing (AM) because of its excellent weldability and resistance to hot cracking. The extreme processing condition of AM often introduces enormous residual stress (hundreds of MPa to GPa) in the as-fabricated parts, which requires stress-relief heat treatment to remove or reduce the internal stresses. Typical residual stress heat treatment for AM Inconel 625, conducted at 800 °C or 870 °C, introduces substantial precipitation of δ phase, a deleterious intermetallic phase. In this work, we used synchrotron-based in situ scattering and diffraction methods and ex situ electron microscopy to investigate the solid-state transformation of an AM Inconel 625 at 700 °C. Our results show that while the δ phase still precipitates from the matrix at this temperature, the rate is much slower. The precipitate size is much smaller when compared with the same phase precipitated at the typical heat treatment temperatures of 800 °C and 870 °C. A comparison with thermodynamic modeling predictions rationalizes the experimental findings. Our work provides the rigorous microstructural kinetics data required to explore the feasibility of a lower-temperature stress-relief heat treatment for AM Inconel 625. The combined methodology is readily extendable to investigate the solid-state transformation of other AM alloys.
Applied Sciences


additive manufacturing, scattering, synchrotron, in situ, CALPHAD


Zhang, F. , Ilavsky, J. , Lindwall, G. , Stoudt, M. , Levine, L. and Allen, A. (2021), Solid-State Transformation of an Additive Manufactured Inconel 625 Alloy at 700 °C, Applied Sciences, [online],, (Accessed May 26, 2024)


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Created September 23, 2021, Updated November 29, 2022