Abstract:

The most popular marine industry alloy of nickel-aluminum bronze (Cu-9Al-4Ni-4Fe-1Mn) was considered for additive manufacturing (AM) via the selective laser melting (SLM) procedure. Non-equilibrium precipitation of κ-phases upon rapid cooling with the SLM technique was studied using advanced characterization techniques by scanning transmission electron microscopy (STEM) and atom probe tomography (APT). These structural investigations revealed the occurrence of martensitic phase transformation with the super-saturation of elements through the lattice structure upon rapid solidification. Also, the APT analysis interestingly displayed a high fraction of nano-scale Fe-rich clusters inside the martensitic laths in the form of κ_IV precipitates. Based on the evident microstructural features, the results of the present work establish the occurrence of the κ_IV as a non-equilibrium phase with a high probability of formation during rapid cooling in SLM processing in addition to the martensitic phase transformation.

Keywords: Nickel-aluminum bronze (NAB) alloy; Non-equilibrium precipitation; Selective laser melting (SLM); Atom probe tomography (APT).

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Gerhard Wilde