Magnesium (Mg)-based alloys are investigated for the use as lightweight structural metals, e.g., in the automotive industry, [1] as biodegradable implant materials [2] and for hydrogen storage. [3] The choice of alloying system and subsequent processing of the material is a crucial factor for the degradation profile of the alloy and its mechanical properties. [4][5][6][7] This review focuses on use of Mg alloys as implant material, with some references to its application as a structural metal.The degradation profile of Mg alloys is of particular importance for their application as implant materials, as a controlled degradation is required to ensure cell viability and implant stability in vivo. [8,9] During the development of Mg alloys for the application as a biodegradable implant, alloying systems are carefully selected and manufactured, with their microstructure being tailored according to specifications by selecting the appropriate processing route. The microstructure and the mechanical properties of the alloy will be evaluated and the alloy is then tested for in vitro degradation in an aqueous environment under physiological conditions (pH %7.4, 37 C, 5% CO 2 , 21% O 2 , 95% rel. humidity) with and without cells to assess its general degradation properties and cell viability. [10] The mechanical properties and degradation profile need to be tailored depending on the application of the implant. Mg alloys for bone support, for example, require mechanical properties close to that of bone. For bone, the average Young's modulus is between 7 and 31 GPa, depending on the type of bone and its hydration state. [11,12] In longitudinal direction, the bone's tensile and compressive ultimate strength have been reported to be between 93 and 135 MPa, and 154 and 205 MPa, respectively. [13,14] Finally, the elongation to failure of the clinically approved MAGNEZIX screw by Syntellix AG (Hanover, Germany) was determined to be 8%. [15] By contrast, Mg alloys designed for the use as stents must possess a minimum ultimate tensile strength of 300 MPa, low yield strength of 200-300 MPa, and higher ductility (min. 15%-18% elongation to failure, preferably 30%) for their successful deployment. [16,17] Finally, in vivo animal experiments are conducted to evaluate the alloy suitability for the translation into the clinic.
