Microstructural Evolution of Magnetic Ni-Mn-Co-In Alloy Powders for Coatings and/or Additive Manufacturing

Magnetic Ni-Mn-Co-In alloys, belonging to the family of magnetic shape memory alloys, exhibit a reversible martensitic transformation that can be triggered by temperature, stress, or magnetic fields, enabling functional strain and field-responsive behawior [1,2]. Translating these properties to coatings and/or additive manufacturing requires powder feedstocks with controlled phase stability and microstructural robustness, because the alloy system is intrinsically brittle and sensitive to processing-induced cracking. In this work, we investigate how minor alloying additions—representing a light element (B) and a heavy element (Mo)—influence the microstructural evolution and transformation behavior of Ni-Mn-Co-In powders designed for thermal spray and powder-bed processing routes. Powders with 0–4 wt.% additions were produced and subjected to tailored thermal treatments to simulate thermal histories relevant to coating deposition and layer-wise consolidation. Scanning electron microscopy and EBSD reveal a matrix–precipitate microstructure, with addition-rich particles dispersed throughout the powder and evolving in volume fraction with composition. DSC shows systematic shifts of martensitic transformation temperatures by ~50–60 K. Phase constitutions and lattice structures are resolved by XRD and TEM, providing guidance for composition–process windows suitable for functional coatings and additively manufactured components.

[1] K. Ulakko et. al., Mater. J. Mater. Engin. Perform. 5 (1996), 405-409.

[2] R. Kainuma, Y. Imano, W. Ito, Y. Sutou, Nature Vol 439 (2006), 957-960.