9 - Biodegradable magnesium alloys

Abstract

Magnesium (Mg) and its alloys attracted most of the recent attention in research attempting to develop nonpermanent biomedical devices due to their biodegradable nature and acceptable biocompatibility. Also, Mg alloys offer a low modulus of elasticity, close to that of the human bone, and low density resulting in low-weight devices. However, these alloys undergo a considerably fast degradation process in a physiological environment that could limit their biomedical applications. The degradation process may take place in different forms such as galvanic, pitting, and stress corrosion modes. In addition, the relatively low strength of Mg alloys compared to the conventional biocompatible metallic alloys (e.g., Ti-6Al-4V and CrCoMo) limits the use of these alloys to low load-bearing applications. In order to improve their mechanical/chemical functionality and suitability for bio-applications, a deep understanding of various Mg alloys, their fabrication processes, and their capabilities is needed. To this end, this book chapter presents the potential, manufacturing, and properties of Mg alloys for biomedical applications. Researchers have proposed different experimental and numerical methods to achieve an engineered Mg alloy with controlled degradation and mechanical properties after implantation inside the human body. It has been proven that a good selection of alloying elements and manufacturing processes is key to attaining the desired properties and to qualify these materials for biomedical applications. For instance, a set of protective post-processes might be needed to reduce the corrosion rate and to diminish the adverse effects of corrosion byproducts of Mg alloys. These post-processes can be in form of coating deposition, heat treatment, or mechanical/chemical modification of substrates. Besides the experimentations, finite element analysis/modeling (FEA/FEM) can be useful to predict the degradation behavior of Mg alloys in the human body. These modeling processes enable scientists to save time and costs. However, a number of factual data-sets are needed to sharpen the prediction models and simulations, which have to be provided by experimental investigations. Simultaneous consideration of material science, fabrication methods, characterization techniques, and numerical analyses of Mg-based alloys is crucial to achieve the ultimate engineered functionality of a designed implant.