The demand for advanced clinical treatments for a range of soft and hard tissue injuries and diseases has led to the use of innovative bioresorbable metallic implant materials. These materials, which undergo degradation over time, can prevent long-term complications and revision surgeries associated with permanent implants. Besides magnesium- and zinc-based systems, iron-based alloys are attractive candidates for degradable medical devices [1]. For the latter, especially Fe-Mn-C alloys are promising as they offer a favourable combination of high ductility, strength, and processability making them suitable for delicate implant designs such as stents. Therefore, understanding and tailoring the processing route, its impact on the Fe-Mn-C alloy’s microstructure and their resulting mechanical and corrosion properties are essential for successful materials development. Additionally, by achieving the fabrication of comparable microstructures, the effect of different alloy compositions on the properties is studied. This enables the selection of the most favourable material for a potential medical application.

This study presents the characterization of promising Fe-Mn-C compositions, which were fabricated by vacuum induction melting, homogenization and hot forging. The microstructure was analysed by scanning electron microscopy (SEM) including electron backscatter diffraction (EBSD) and was verified to be austenitic with comparable grains size for the studied alloys. The mechanical properties were investigated under uniaxial tensile load and show both, enhanced strength as well as ductility, especially in comparison to as-cast counterparts, see figure 1 [2]. The intrinsic elastic material properties which are meaningful for the recoil behaviour of stents were investigated by means of ultrasonic testing. The in-vitro corrosion behaviour of the Fe-Mn-C alloys was characterized electrochemically in simulated body fluids under well-defined hydrodynamic flow. The degraded surfaces were studied spectroscopically to gain further insight into the corrosion mechanisms. As a result, improved mechanical and degradation properties are observed, which flattens the path to the intended vascular implant application.

References

[1] H.S. Han, Materials Today, 2019, 23, 57–71.

[2] J. Hufenbach, , Materials and Design, 2018, 142, 22–35.