Micro- and nanostructure of additively manufactured,in-situ alloyed, magnetic spinodal Fe₅₄Cr₃₁Co₁₅

Exploring the chemical micro- and nanostructure of metal alloys is essential to
understand their physical properties, such as magnetism or hardness. Additively
manufactured (AM) materials, e.g. via laser powder bed fusion (LPBF)
followed by various heat treatments, can raise further questions concerning the
printed material. For the in-situ alloyed, spinodal Fe54Cr31Co15 system, the
macroscopic magnetic behaviour is greatly influenced by subsequent
homogenisation and heat treatment steps. Here we show that the decomposition
takes place on the nanometre scale, resulting in ferromagnetic FeCo-rich particles
embedded in a Cr-rich matrix. By studying phenomena like chemical
homogeneity, grain structure, and texture of the in-situ alloyed material at
different scales, we reveal correlations between the heat treatment and the
resulting nanostructure and its ferromagnetic properties. We found that the
isothermal heating conditions determine the degree of phase segregation and
that a homogenization step can be omitted for additively manufactured, in-situ
alloyed FeCrCo alloys. The approach thereby offers insight and a path for also
tailoring specific manufacturing parameters to provide the right quality printed
materials with desired functionalities. For example, magnetic FeCrCo alloys are
often used in electric motors or magnetic sensors, and the flexibility of the
presented approach can lead to optimal use of the material.