Tang, Y T; Panwisawas, C; Jenkins, B M; Liu, J; Shen, Z; Salvati, E; Gong, Y; Ghoussoub, J N; Michalik, S; Roebuck, B; Bagot, P A J; Lozano-Perez, S; Grovenor, C R M; Moody, M P; Korsunsky, A M; Collins, D M; Reed, R C (2023) Multi-length-scale study on the heat treatment response to supersaturated nickel-based superalloys: Precipitation reactions and incipient recrystallisation. Additive Manufacturing, 62. 103389 ISSN 22148604

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Abstract

A supersaturated � phase microstructure is produced in Ni-based superalloys using laser powder bed fusion (LPBF) – the cooling rate arising from the process is shown to suppress the solid-state precipitation of the �′ phase. The response of the material to a heat treatment therefore requires new understanding at the fundamental level, since the first population of �′ precipitate forms upon heating, in contrast to cooling from homogenisation above the �′ solvus. Here, we have interrogated two new nickel-based superalloys designed for the L-PBF technology, both in situ and ex situ, at multiple length scales using advanced characterisation methods. First, we conducted in situ synchrotron X-ray diffraction during various heat treatments to trace the evolution of the �′ volume fraction with temperature. The first structural changes were detected at an unexpectedly low temperature of ∼445 ◦C. Second, the temperature for �′ nucleation and its sensitivity to heating rate was studied using an electrical resistivity method. Then, the �′ composition upon heating, isothermal holding and cooling is analysed using atom probe tomography (APT), the result is rationalised by further scanning-transmission electron microscopy and nanoscale secondary ion mass spectroscopy. Finally, static recrystallisation during isothermal exposure was investigated, which occurs within minutes. This work sheds light on a new strategy of tailoring microstructure for additively manufactured superalloys by manipulation of the �′ precipitate distribution upon heating.

Item Type:	Article
Keywords:	Precipitation kinetics, Recrystallisation, Additive manufacturing, Synchrotron, Superalloys, Atom probe tomography, Non-equilibrium
Subjects:	Advanced Materials > Metals and Alloys
Divisions:	Materials and Mechanical Metrology
Identification number/DOI:	10.1016/j.addma.2023.103389
Last Modified:	04 Nov 2026 11:35
URI:	https://eprintspublications.npl.co.uk/id/eprint/10580