Nanoscale Magnetic Properties of Additively Manufactured FeCoNiAl_xMn_x High-Entropy Alloys

Abstract

Magnetic properties of High-Entropy Alloys based on the Fe-Co-Ni-Al-Mn system are reported. High-Entropy Alloys are cutting-edge technological materials containing five or more elements in relatively high concentrations (5-35 at.%) within one or several solid-state solutions. These solutions are stabilized at the nanometer scale due to the high contribution of the mixing entropy to the Gibbs free energy, which can overcome the enthalpic contribution. Two magnetic alloys are found in FeCoNiAlxMnx (1.6 at.%  x  7.8 at.%) samples processed by laser metal deposition. The magnetic techniques used to screen the materials were magneto-optical imaging and magnetic force microscopy. The former allows characterizing magnetic properties within the mm-μm scale, while the latter is efficient down to the nanometer scale. Magnetic screening confirms the importance of the nanostructure in defining magnetic properties of the alloys, and the trends in the magnetic behavior as a function of the alloy composition are revealed. The experimental results suggest that it is possible to form unique alloys, which may outperform conventional magnetic materials used in a variety of applications such as transformers, screening shields and wind power generators.

Identifying Magnetic Phases in Additively Manufactured High-Entropy Alloy FeCoNiAlxMnx

“…Similar phase transitions regarding the same system were also postulated by other works [9]. The study in [5], also on the FeCoNiAlxMnx system, was mainly focused on intermediate and low concentrations of Al and Mn. Extending this range, three samples of different concentrations, high, low and intermediate have been investigated by magnetic force microscopy (MFM) and energy dispersive x-ray analysis (EDX) on a scanning electron microscope (SEM).…”

“…The recently emerged new class of materials, High Entropy Alloys (HEAs), is attracting considerable attention due to the formation of unexplored phases stabilized by the high mixing entropy [1]. Some of these phases have -among others-unique mechanical [2][3][4] or interesting magnetic [5][6][7] properties. The magnetically strong and relatively inexpensive materials, Fe, Co and Ni were chosen to coexist with Al and Mn.…”

“…The choice of Al and Mn is not accidental, as it is known that, although they are non-magnetic as individual elements, in combination with each other they form strong ferromagnetic compounds [8]. The parametric modelling presented in [5] shows that in a certain range of Al and Mn content, FeCoNiAlxMnx exhibits a tendency to form two separate phases. At high concentration of Mn and Al, a body-centered cubic ordered alloy is expected, whereas at low Al and Mn contents, a face-centered cubic phase is mainly predicted.…”

Emerging Functional Metals in Additive Manufacturing

“…Another way is the weight-controlled blending of elemental powders in order to obtain the desired composition. [86,87] However, this can result in a multimodal particle size distribution (PSD) with variable particle morphologies and densities. [88] Moreover, blending might lead to inhomogeneity in the final built part's structure, since the melt pool in L-PBF is small and the ratio of elements might not be homogenous across the powder bed.…”

Synthesis of High Entropy Alloy Nanoparticles by Pulsed Laser Ablation in Liquids: Influence of Target Preparation on Stoichiometry and Productivity

“…Downsizing HEAs to the nanoscale provides additional application possibilities resulting from the high surface‐to‐volume ratio and quantum confinement effect, making them suitable for catalysis [12–15] energy storage, [16,17] magnetic, [18–20] and biomedical applications [21,22] . Feng et al [12] .…”