Microstructure, Shape Memory Effect, Chemical Composition and Corrosion Resistance Performance of Biodegradable FeMnSi-Al Alloy

Abstract

The medical applications of degradable iron-based biomaterials have been targeted by re-searchers due to their special properties that they present after alloying with various elements and different technological methods of obtaining. Compared to other biodegradable materials, iron-based alloys are designed especially for the low production costs, the non-magnetism obtained by alloying with Mn, and the shape memory effect (SME) following the alloying with Si, which is necessary in medical applications for which it could replace nitinol successfully. Alloying with new elements could improve the mechanical properties, the degradation rate, and the transformation temperatures corresponding to the SME. This paper presents the results from the study of FeMnSi-Al alloy as a biodegradable material. The X-ray diffraction (XRD) method was used to identify the phases formed in the experimental Fe-Mn-Si-Al alloy, and the SME was studied by differential scanning calorimetry (DSC). In vitro tests were performed by immersing the samples in Ringer’s biological solution for different time intervals (1, 3, and 7 days). The chemical composition of the samples, as well as the compounds resulting from the immersion tests, were evaluated by energy dispersive X-ray (EDS). Scanning electron microscopy (SEM) was used for the microstructural analysis and for highlighting the surfaces subjected to contact with the electrolyte solution. The corrosion rate (CR, mm/yr.) was calculated after mass loss, sample surface area, and immersion time (h) (at 37 °C). Samples were subjected to electro-corrosion tests using electrochemical impedance spectroscopy (EIS) and Tafel linear and cyclic potentiometry.

Microstructural and Electrochemical Influence of Zn in MgCaZn Biodegradable Alloys

“…To make the samples more electrically conductive, a Luxor Au SEM COATER—CT-2201-0144 (Kusterdingen, Germany) was used to deposit a 5 nm coating of gold to the surface and cross-section of the samples. An SEM FEI Quanta 200 3D microscope (Brno, Czech Republic) with the following specifications was used: Low vacuum mode, LFD (large field detector), HV (high voltage): 20 kV, WD (working distance): 10 mm, comparable to previous research [ 28 ], and a Vega TESCAN LMHII SEM microscope (Brno, Czech Republic) with the following parameters [ 29 ]: secondary electrons (SE) detector, electron gun supply: 30 kV, high vacuum, and 15.5 mm working distance. X-ray diffractions were performed using a Panalytical Xpert PRO MPD 3060 (Almelo, The Netherlands) facility equipped with a Cu X-ray tube (K = 1.54051), 2Theta: 20°–90°, step size: 0.13°, time/step: 51 s, and a scan speed of 0.065651°/s in the reflection mode.…”

Analysis of Degradation Products of Biodegradable ZnMgY Alloy

“…It was observed that the main corrosion products passed from the surface into the solution during the immersion and cleaning steps. As the surface was covered with ZnO, which was the main corrosion product, a protective layer was formed at the beginning [74]. The zincite layer was repeatedly formed, and was penetrated by various ions in the electrolyte solution.…”

Investigations on the Degradation Behavior of Processed FeMnSi-xCu Shape Memory Alloys

“…This alloy belongs to the biodegradable materials class and can be functionalized considering SME for specific medical applications. Each of these classes of biodegradable alloys has advantages and disadvantages in terms of DR, mechanical properties and SME [ 5 ]. Mg-based alloys show both biocompatibility and good mechanical properties [ 6 , 7 , 8 , 9 , 10 , 11 ], but the DR is very high and hydrogen gas evolution has been observed in degradation [ 12 ].…”