Search

In recent years, more attention to unique and complex structures, such as nature-inspired and porous structures for medical applications, has been strongly developed. Open-cell porous metal-based ones display more benefits than rigid ones since they facilitate the transformation of load between the bone and the implants and avoid the phenomenon of stress shielding and bone resorption. By being biodegradable and non-toxic, as well as having lower density and mechanical properties close to those of natural bone, Mg and its alloys are considered promising materials for porous scaffolds. However, a high corrosion rate is the main drawback of Mg alloys. The porosity of porous structures can also worsen it as it enhances the surface area exposed to the corrosive solution and negatively impacts the performance of porous structures, that these issues have not been addressed in detail so far. Since fabrication methods of Mg-based scaffolds can significantly affect the porosity-related properties (e.g., porosity percentage, type, size, and geometry) and, consequently, scaffolds' mechanical behavior and corrosion resistance, this paper reviews and compares the fabrication methods of porous structures and how they affect the resultant properties. However, among different methods, due to the expansion of additive manufacturing as a novel and exciting manufacturing technique, the paper's central focus is on using additive manufacturing in biomedical applications, discussing its advantages over other techniques. The effect of geometrical parameters on mechanical properties and corrosion rate, which strongly affects bio-application, are also given. Moreover, different strategies are briefly introduced for tailoring the high corrosion rate of Mg and its alloys, such as alloying elements and coatings. However, there is still less information regarding the additive manufacturing of porous Mg scaffolds and the optimum way of controlling the corrosion rate of Mg-based parts. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure, mechanical properties, corrosion behavior of as-cast Mg–1.8Zn–0.4Zr–1.74Gd–xY (x = 0, 0.25, 0.5, 0.75, 1.0, 1.25 wt%) biodegradable magnesium alloys. Microstructures of the alloys were characterized by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the alloys were mainly composed of α-Mg matrix (Mg, Zn)3(Gd, Y) phase, Mg3Zn3(Gd, Y)2 phase and Mg12Zn(Gd, Y) phase. It was found that 0–1.25 wt% Y addition led to significant grain refinement of the alloys from 111.5 to 57.3 μm. Moderate amount of Y resulted in improved strength. However, the strength and elongation decreased when the Y content exceeded 0.5 wt%. With 0.5 wt% of Y, the corrosion rate and corrosion current density were 0.721 ± 0.042 mm y−1 and 4.76 μA cm−2, respectively, which were lower than the other investigated alloys. Among all the tested samples, Mg–1.8Zn–0.4Zr–1.74Gd–0.5Y alloy has the moderate corrosion rate and mechanical properties, making it promising for the future optimization of the biodegradable Mg–Zn–Zr–Gd–Y alloys. [ABSTRACT FROM AUTHOR]

Magnesium-based alloys presented great potential for biodegradable implant materials. However, the poor mechanical properties and high corrosion rate blocked its extensive application. In this study, a new biodegradable Mg–Zn–Y–Gd–Zr alloy was fabricated and extruded. The microstructure, corrosion morphologies and corrosion products film of the as-cast, homogenized and as-extruded alloys were characterized by optical micrographs, scanning electron microscopy, X-ray diffraction and laser scanning confocal microscopy. Moreover, the corrosion mechanisms of the as-cast and as-extruded alloys were proposed, and the influencing factors of corrosion properties were discussed. The electrochemical test, immersion tests and corrosion morphologies demonstrated that the as-extruded alloy exhibited favorable corrosion properties. The as-cast and homogenized alloys displayed localized corrosion mode, and the as-extruded alloy displayed uniform corrosion mode. The Volta potential of the Mg3(Y,Gd)2Zn3 phase relative to Mg matrix was measured by using Kelvin probe force microscopy. [ABSTRACT FROM AUTHOR]