Liquid metal dealloying is a novel technique for elaborating micro and nano-porous materials composed by connected ligaments forming an open porosity. It consists in immersing an AB precursor alloy into a liquid metal C with A and B respectively immiscible and miscible into C. Upon the dissolution of B in C, A reorganizes into a fine porous structure. This work aims at using liquid metal dealloying to elaborate nanoporous powders with extended surface area and controlled mechanical properties for potential applications as catalysts or additive manufacturing processes. Partially dealloyed powders with a porous shell and a solid core are foreseen as an innovative material for coating techniques, in particular cold spray. Their dual core-shell structure is expected to favor the adhesion of powders on the coated surface.

Focusing on the FeNiMg system (Fe=A, Ni=B, Mg=C), Inconel 718 and Invar Fe₆₄Ni₃₆ were dealloyed in liquid Mg. Precursor powder and Mg powder were homogeneously mixed and heated using a Spark Plasma Sintering (SPS) apparatus above T_m^Mg=650°C. After the dissolution of Ni in Mg, samples were etched in nitric acid (HNO₃) to remove Mg-containing phases and obtain porous powders. Our experiment shows that adjusting the precursor / bath ratio enables to elaborate partially dealloyed powders. The dealloyed fraction was characterized through various techniques: SEM, X-ray tomography and X-ray diffraction.

To better predict and control the dealloyed fraction and the composition of the resulting phases without relying on computationally expensive phase-field modelling, we also developed a 1D diffusion model incorporating the thermodynamic assessment of the system: it relies on the integration of Fick-Jacobs equation for the diffusion in channels of varying cross-sections and on the computation of the thermodynamic equilibria between solid and liquid phase in the dealloyed layer. This model was applied to study the dealloying of NiCuAg system (Ni=A, Cu=B, Ag=C) and demonstrates a semi-quantitative agreement with experimental results, without the adjustment of fitting parameters.