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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.

Fe–Mn alloys are promising candidates for less-invasive and temporary implants such as bioabsorbable stents. However, their composition and microstructure must be tailored to assess an adequate corrosion rate for the desirable lifespan of the stent. This study aimed to evaluate the development of Fe–Mn alloy and its structure and properties correlation when processed by electrodeposition. Planar samples were produced by potentiostatic deposition at two different potentials, −1.3 and −1.7 V vs. Ag/AgCl, from a chloride-based acidic electrolyte with different amounts of NH4Cl. It was verified that, in more negative deposition potentials, the deposition interface changes from planar to dendritic, leading to more ramified deposits with a high level of defects like cracks and pores. More negative potentials also increased the Mn content in the deposit from 0.8 to 5.2 wt.% Mn. The microstructure was composed of a single phase of (Fe, Mn) solid solution in the −1.3 V vs. Ag/AgCl deposit, while the deposit obtained at −1.7 V vs. Ag/AgCl exhibit two phases, one rich in Mn and the other rich in Fe. A higher concentration of NH4Cl in the electrolyte leads to an increase in the Mn content (5.2 wt.% Mn), maintaining the monophasic microstructure. Although several challenges still remain, these results prove that is possible to obtain Fe–Mn bioabsorbable alloys by electrodeposition, which opens a new processing route for these alloys.

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 present work aims at exploring the influence of laser welding on the functional behaviour of a Fe-20Mn-0.6C (wt.%) bioabsorbable alloy. At first, the selection of the most suitable process speed (40 mm/s) was done in order to obtain a full penetration joint with limited taper. Then, microstructural and mechanical analyses of welded sheets confirmed suitable performance of the joint, without porosity, thus preserving chemical composition, mechanical resistance and ductility even after welding. In particular, the base material comprised both γ austenite and ε martensite, while the welded samples showed a further type of martensite, namely α’. Moreover, ultimate tensile strength (1095 MPa and 1104 MPa in base and welded material, respectively) and elongation to failure (61.3% and 60.9%, respectively) were almost not influenced by the welding process. Considering the absorbable nature of these alloys, static immersion degradation tests were carried out, and confirmed that the surface of the welded bead did not exhibit a significant variation of the material degradation rate after 14 days in modified Hanks’ solution. Finally, a significant accumulation of degradation products, mainly (Fe,Mn)CO3, was observed along the joining line.

• Synthesis of Fe-35Mn-5Si powder by ball milling to get single austenitic phase. • Consolidation by spark plasma sintering at 650 °C to achieve density ≥ 98% • Degradation rate comparable to existing Fe-Mn based alloys. • Superior mechanical and magnetic properties compared to existing implant materials. • Application in biodegradable cardiovascular and orthopaedic implants. Biodegradable metals are emerging as novel implant materials by overcoming the drawbacks of the existing materials used commercially. This work investigates the suitability of Fe-35Mn-5Si as a biodegradable implant by examining its mechanical and corrosion behavior. The processing involves High Energy Ball Milling (HEBM) followed by Spark Plasma Sintering (SPS) and heat treatment at optimized conditions to develop a single-phase austenitic alloy. The heat-treated (HT) samples exhibited low magnetic susceptibility of 3.47x10−7 due to the austenitic phase formation. Yield strength of 500 MPa, UTS of 712 MPa, Young's modulus of 110 GPa, and hardness of 380 HV along with 9.5% elongation was obtained in the optimized samples, which are comparable to Ti alloy and 316L stainless steel metallic implants. The corrosion tests yielded degradation rates of 0.025 mm/year for the alloy in standard Hank's solution. This alloy could pave the way for the fabrication of low-cost biodegradable implants using the simple powder metallurgy route. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the sublimation of Mn and microstructural evolution of binary Fe/Mn compacts sintered at various temperatures in a vacuum. A high sintering temperature or a lengthy holding time promotes powder densification. Due to sublimation of Mn, the weight loss of the compacts mainly occurs during the isothermal holding stage of the sintering process; it increases significantly from 1.5 wt.% for sintering at 1000 °C to 8.6 wt.% at 1200 °C. For the first time, the phase evolution in the binary elemental compacts was clarified using in situ neutron diffraction. The γ-austenite phase emerges during temperature ramping to 536 °C, while β-Mn and α-Fe disappear at 774 °C and 881 °C. The neutron diffraction also revealed that single phase γ-austenite forms in the Fe-Mn compacts if the temperature is ≥ 881 °C. Highlights • In situ and real-time neutron diffraction was used to identify phase transition. • Sublimation behavior of Mn in Fe/Mn powder mixtures was investigated. • The sintered microstructure is related to sublimation of Mn. [ABSTRACT FROM AUTHOR]

The effect of severe plastic deformation, namely, high-pressure torsion (HPT) at different temperatures and ball milling (BM) at different time intervals, has been investigated by means of Mössbauer spectroscopy in Fe100–xMnx(x = 4.1, 6.8, 9) alloys. Deformation affects the short-range clustering (SRC) in BCC lattice. Two processes occur: destruction of SRC by moving dislocations and enhancement of the SRC by migration of non-equilibrium defects. Destruction of SRC prevails during HPT at 80–293 K; whereas enhancement of SRC dominates at 473–573 K. BM starts enhancing the SRC formation at as low as 293 K due to local heating at impacts. The efficiency of HPT in terms of enhancing SRC increases with increasing temperature. The authors suppose that at low temperatures, a significant fraction of vacancies are excluded from enhancing SRC because of formation of mobile bi- and tri-vacancies having low efficiency of enhancing SRC as compared to that of mono vacancies. Milling of BCC Fe100–xMnxalloys stabilises the BCC phase with respect toα → γtransition at subsequent isothermal annealing because of a high degree of work hardening and formation of composition inhomogeneity. [ABSTRACT FROM AUTHOR]

The effect of C on the damping and mechanical properties of thermally trained Fe-17 wt%Mn- X wt%C (0< X <0.06) high-damping alloys was analyzed by the impulse internal friction technique and uniaxial tensile tests. The alloys were subjected to a combination of thermo-mechanical processing and thermal cycling which resulted in a C content independent phase fraction and grain size of ɛ-martensite and γ-austenite. The ɛ↔γ phase transformation and the anti-ferromagnetic transition in the γ-phase were observed in the temperature-dependent damping and modulus measurements, respectively. While C had no influence on the intrinsic internal friction of the γ-phase, small amounts of C significantly reduced the damping associated with the motion of ɛ-γ interface boundaries and the widening of stacking faults by the movement of partial dislocations. The C content at which these relaxation processes were suppressed, i.e. approximately 0.03 wt%C, coincided with the onset of dynamic strain aging as inferred from the appearance of serrations on the flow curves. [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]

The deformation-intensified atomic Mn-related separation of the bcc solid solution has been found in FeMn alloys ( x = 4.5-9.9) subjected to ball milling using Mössbauer spectroscopy. In the near surrounding of iron atoms, the atomic separation is similar to that observed upon the annealing of the alloys in a temperature range of 400-500°С. It has been found that the deformation-intensified atomic separation leads to the stabilization of the bcc phase with regard to the α → γ transformation, as well as to the expansion of the field of the existence of the bcc phase during heating. [ABSTRACT FROM AUTHOR]