Nickel aluminides reinforced with a ductile (Cr,Mo) phase are a novel class of high-temperature materials, promising a low density and good corrosion resistance. However, their ductility and creep strength are still limited. Additive manufacturing via electron beam powder bed fusion (PBF-EB) offers new opportunities for processing this material class: the high-temperature process is well-suited for processing crack-prone materials such as NiAl into near-net-shape geometries, and the high solidification rates create fine microstructures. In this study, we establish the first processing window for PBF-EB processing of a fully eutectic NiAl-(Cr,Mo) alloy and explore the effects of processing parameters on the microstructure and its evolution during the in-situ heat treatment characteristic of the process. The initial microstructure after melting exhibits a unique network-like, interpenetrating structure of NiAl and (Cr,Mo) phases. The size of the (Cr,Mo) phase increases with increasing energy input. Prolonged exposure to processing temperatures above 1000 °C leads to continuous coarsening of the phase network by a factor of 7, as well as discontinuous coarsening (DC). The DC reaction follows a Johnson-Mehl-Avrami-Kolmogorov pattern and stabilizes after several hours. The final fraction of discontinuously coarsened microstructure is determined by the choice of processing parameters. Furthermore, the DC reaction initiates at grain boundaries, thereby leading to grain refinement during coarsening. This refinement ensures a texture-free, fine-grained microstructure. Tuning the PBF-EB process parameters thus allows tailoring the microstructure of the NiAl-(Cr,Mo) alloy by selecting appropriate (Cr,Mo) phase sizes and DC fractions and provides a path to optimizing the alloy’s mechanical properties. • Successful processing of an intermetallic NiAl-(Cr,Mo) in-situ composite • Microstructure consists of interconnected and discontinuously coarsened regions • Adaptable, texture-free, homogeneous microstructure is achievable • Phase and grain structure can be tailored by adjusting the processing parameters
Fiegl et al. (2026) studied this question.