Modification of Biocorrosion and Cellular Response of Magnesium Alloy WE43 by Multiaxial Deformation

The study shows that multiaxial deformation (MAD) treatment leads to grain refinement in magnesium alloy WE43. Compared to the initial state, the MAD-processed alloy exhibited smoother biocorrosion dynamics in a fetal bovine serum and in a complete cell growth medium. Examination by microCT demonstrated retardation of the decline in the alloy volume and the Hounsfield unit values. An attendant reduction in the rate of accumulation of the biodegradation products in the immersion medium, a less pronounced alkalization, and inhibited sedimentation of biodegradation products on the surface of the alloy were observed after MAD. These effects were accompanied with an increase in the osteogenic mesenchymal stromal cell viability on the alloy surface and in a medium containing their extracts. It is expected that the more orderly dynamics of biodegradation of the WE43 alloy after MAD and the stimulation of cell colonization will effectively promote stable osteosynthesis, making repeat implant extraction surgeries unnecessary.

Elucidating the Effect of Additive Friction Stir Deposition on the Resulting Microstructure and Mechanical Properties of Magnesium Alloy WE43

In this work, the effect of processing parameters on the resulting microstructure and mechanical properties of magnesium alloy WE43 processed via Additive Friction Stir Deposition (AFSD), a nascent solid-state additive manufacturing (AM) process, is investigated. In particular, a parameterization study was carried out, using multiple four-layer deposits, to identify a suitable process window for a structural 68-layers bulk WE43 deposition. The parametric study identified an acceptable set of parameters with minimal surface defects and excellent consolidation for the fabrication of a bulk WE43 deposition. Microstructural, tensile, and fatigue life characterization was conducted on the bulk WE43 deposition and compared to commercially available wrought material to elucidate the process-structure-property-performance (PSPP) relationship of the AFSD process. This study shows that the bulk WE43 deposit exhibited a refined homogenous microstructure and a texture shift relative to the wrought material. However, a reduction in hardness and tensile behavior was observed in the as-deposited WE43 compared to the wrought control. Additionally, fatigue specimens extracted from the bulk deposition exhibited a decrease in life in the low-cycle regime but performed comparably to the wrought plate in the high-cycle regime. The outcomes of this study illustrate the potential of the AFSD process in additively manufactured structural load-bearing components made with magnesium alloy WE43 in the as-built condition.

Influence of pH on corrosion resistance of electrodeposited Mg-Fe LDH composite films on Mg alloys WE43

Layered double hydroxide (LDH) are widely studied as corrosion inhibition coatings for magnesium (Mg) alloys due to their nano-lamellar structure and anion-exchange ability. The two common approaches in synthesising LDH films on Mg alloys are co-precipitation and hydrothermal treatment. Recently, electrodeposition has drawn more interest as a potential synthesis approach due to the low cost, ease of control, one-step method, and ability to create a compact film. In this work, Mg-Fe LDH film was synthesised on magnesium hydroxide, Mg(OH)2 layer formed on Mg alloy WE43 by electrodeposition approach with the as-prepared iron solution at different pH values. The effect of pH of the solution (3.0, 5.0 and 7.0) on the formation of LDH films was investigated using Field Emission Scanning Electron Microscopy (FESEM). Additionally, the surface chemical components of the film were obtained by Fourier Transform Infrared Spectrometer (FTIR). All the LDH composite films synthesised at different pH values undergo electrochemical tests in Hank’s Balanced salt solution (HBSS). All samples promote corrosion resistance of WE43 with the LDH film synthesised at pH 3.0 provided the highest inhibition efficiency (I.E) of 94.48 % and resistance polarisation value of 3559. 07 Ωcm2.

THE EFFECT OF MULTIAXIAL DEFORMATION ON THE DYNAMICS OF BIODEGRADATION AND CELL COLONIZATION OF ALLOY WE43

Introduction. The development of materials for bioresorbable implants is an urgent issue in medicine and materials science. Magnesium alloys are promising materials for this purpose. In particular, alloy WE43 (Mg-Y-Nd-Zr) has proven itself well in this field. However, the use of magnesium alloys is limited by a high degradation rate, which is often accompanied with nonuniform corrosion, which negatively affects the load bearing capacity of the product. In addition, the increased degradation rate usually seriously worsens the biocompatibility of magnesium alloys. Therefore, the study of the corrosion resistance of magnesium alloys, as well astheir biocompatibility, is an urgent task.Purpose of the study was to investigate the effect of multiaxial deformation (MAD), aimed at increasing the mechanical characteristics of the alloy WE43, on its biodegradation kinetics, as well as on cell colonization.Materials and methods. The alloy WE43 in two states – homogenized (WE43 hom) and strengthened by MAD (WE43 MAD) was investigated in this work. The kinetics of biodegradation was investigated on an xCELLigence RTCA Systems analyzer. A method for estimating the volume of hydrogen was used to study the process of gas formation, which was recorded using an automated digital microscope LionheartTM FX. The corrosive medium was a solution based on Dulbecco’s Modified Eagle’s Medium. A culture of mesenchymal multipotent stromal cells was used to study the colonization of the alloy surface by cells.Results. MAD of the alloy WE43 leads to a decrease in the biodegradation rate and the intensity of gas formation. The period of stabilization of biodegradation for the alloy after the MAD is 16 hours versus 3 hours for the alloy after homogenization. In this case, the volume of released hydrogen was 65.0 ± 4.4 mm3H2/mm3 alloy and 211.0 ± ± 21.1 mm3H2/mm3 alloy for the alloy after MAD and homogenization, respectively. MAD improves the biocompatibility of the alloy WE43, stimulating the colonization of mesenchymal multipotent stromal cells.Conclusion. MAD reduces biodegradation and improves the biocompatibility of the alloy WE43, which makes it a promising medical material, including for the purposes of oncoorthopedics

Assessment of Galvanostatic Anodic Polarization to Accelerate the Corrosion of the Bioresorbable Magnesium Alloy WE43

In the field of surgery, bioresorbable magnesium is considered a promising candidate. Its low corrosion resistance, which is disadvantageous for technical application, is advantageous for surgery since the implant fully degrades in the presence of the water-based body fluids, and after a defined time the regenerating bone takes over its function again. Therefore, knowledge of the corrosion behavior over several months is essential. For this reason, an in vitro short-time testing method is developed to accelerate the corrosion progress by galvanostatic anodic polarization without influencing the macroscopic corrosion morphology. The initial corrosion rate of the magnesium alloy WE43 is calculated by detection of the hydrogen volume produced in an immersion test. In a corresponding experimental setup, a galvanostatic anodic polarization is applied with a three-electrode system. The application range for the polarization is determined based on the corrosion current density from potentiodynamic polarization. To correlate the initial corrosion rate, and accelerated dissolution rate, the corrosion morphologies of both test strategies are characterized by microscopy images, as well as energy dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. The results demonstrate that the dissolution rate can be increased in the order of decades with the limitation of a changed corrosion morphology with increasing polarization. With this approach, it is possible to characterize and exclude new unsuitable magnesium alloys in a time-efficient manner before they are used in subsequent preclinical studies.

Development of a Laser Powder Bed Fusion Process Tailored for the Additive Manufacturing of High-Quality Components Made of the Commercial Magnesium Alloy WE43

Additive manufacturing (AM) has become increasingly important over the last decade and the quality of the products generated with AM technology has strongly improved. The most common metals that are processed by AM techniques are steel, titanium (Ti) or aluminum (Al) alloys. However, the proportion of magnesium (Mg) in AM is still negligible, possibly due to the poor processability of Mg in comparison to other metals. Mg parts are usually produced by various casting processes and the experiences in additive manufacturing of Mg are still limited. To address this issue, a parameter screening was conducted in the present study with experiments designed to find the most influential process parameters. In a second step, these parameters were optimized in order to fabricate parts with the highest relative density. This experiment led to processing parameters with which specimens with relative densities above 99.9% could be created. These high-density specimens were then utilized in the fabrication of test pieces with several different geometries, in order to compare the material properties resulting from both the casting process and the powder bed fusion (PBF-LB) process. In this comparison, the compositions of the occurring phases and the alloys’ microstructures as well as the mechanical properties were investigated. Typically, the microstructure of metal parts, produced by PBF-LB, consisted of much finer grains compared to as-cast parts. Consequently, the strength of Mg parts generated by PBF-LB could be further increased.