Multimodal γ′ precipitation in Inconel-738 Ni-based superalloy during electron-beam powder bed fusion additive manufacturing
N. Haghdadi, E. Whitelock, B. Lim, H. Chen, X. Liao, S.S. Babu, S.P. Ringer, S. Primig
Journal of Materials Science 55 (2020) 13342–13350.
This paper the first publication from our AUSMURI grant on the role of interfaces during additive manufacturing, and a collaboration with Prof. S.S. Babu, the lead researcher of our US-based MURI counterpart. It is also Sophie's debut in Journal of Materials Science.
Additive manufacturing is a promising alternative method for fabricating components of Ni-based superalloys which are difficult to cast, form and join. However, typical thermal cycles associated with laser powder bed-fusion techniques suppress the formation of desirable microstructures containing γ′ particles, necessitating long-time post-process heat treatments. Here we report in-situ precipitation of γ′ (L12-ordered) particles and carbides during electron-beam powder bed-fusion of Inconel-738. The γ′ particles are homogenously distributed across the build and exhibit a multimodal size distribution. Based on atom-probe microscopy, we propose a eutectic reaction and multiple nucleation, growth, coarsening and dissolution bursts during thermal cycling as formation mechanism.