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Deep eutectic solvents (DESs) are green anhydrous solvents that have recently been proposed in sustainable non-aqueous metal electrodeposition processes. The use of DESs over aqueous solutions allows metal electrodeposition without significant side reactions, such as the evolution of hydrogen gas, which is responsible for embrittlement phenomena. In the current work, the electrolytic deposition of Fe-Mn alloys, which present good application in temporary biomedical devices, using DESs was assessed. Three DESs were studied: (a) choline chloride and ethylene glycol (ChCl/EG), (b) choline chloride and glycerol (ChCl/Gly), and (c) choline chloride and urea (ChCl/Urea). The physicochemical properties (viscosity and conductivity) of the three DESs of interest, with and without the presence of dissolved Fe and Mn salts, were thoroughly studied. Cyclic voltammetry analyses showed that the reduction potential of both metals was within the potential window for the three DESs studied, which allowed the successful electrodeposition of Fe-Mn alloys. The deposit obtained from the ChCl/Urea DES presented the highest amount of Mn (49.71 at%). The latter, as well as the fact that the ChCl/Urea based electrolyte showed good stability at T = 80 °C after four electrodeposition cycles, are promising indicators of the potential success of the use of non-aqueous electrodeposition of Fe-Mn alloys using DESs.

As biodegradable materials, Fe–Mn alloys have a lot of promise, particularly because they can be employed as metallic implants with excellent mechanical properties. Besides allowing for patient customisation, powder-bed fusion of these alloys could help overcome their main drawback, i.e., slow degradation inside the human body, by increasing the component surface with inbuilt structural porosity. The quality of additive-manufactured products depends on their temperature history, making knowledge of the heat-transfer characteristics of the powder-bed fusion process very important. While accurate determinations of temperature gradients and the melt-pool sizes still represent a considerable challenge for all materials, this is particularly true for Fe–Mn alloys, where research is currently limited to a handful of pioneering works, and experimental determinations of the melt-pool contours prove extremely difficult and unreliable. To explore the origins of measurement inconsistency, melt-pool compositions of Fe–Mn specimens were analysed in the scope of this research. Concentric patterns of high- and low-Mn content practically indistinguishable from the melt-pool boundary on the macroscale were revealed within the melt-pool. A microscopic analysis of elemental content distribution was performed and the concentric patterns were attributed to the pronounced segregation of the alloy in conjunction with convective currents. A novel, calibration-free 3D finite-element model of heat transfer during laser powder-bed fusion is proposed to overcome these experimental difficulties and validated against the experimental melt-pool measurements. [ABSTRACT FROM AUTHOR]

The influence of a magnetic transition on Fe and Mn diffusion in bcc Fe–Mn alloys as a function of Mn concentration is studied combining experimental measurements and DFT-informed modeling. The radiotracer technique in combination with precise mechanical sectioning or ion-beam sputtering is used to determine the diffusion rates of 59Fe and 54Mn in a series of Fe–Mn alloys with up to 1.9 at.%Mn. The solvent and solute enhancement factors are determined. While the diffusion rates of Fe atoms are found to be almost independent on the Mn content in the Fe–Mn alloys in both para- as well ferro-magnetic states, Mn diffusion is strongly enhanced by an increase of Mn concentration in these alloys, especially in the paramagnetic state. The experimental findings are supported by theoretical results, which are analyzed in terms of an equilibrium vacancy concentration, atomic jump frequencies, Mn–vacancy binding energy, short-range ordering tendency and kinetic correlation factors. [Display omitted] [ABSTRACT FROM AUTHOR]