Magnesium alloys are the most promising materials for biodegradable medical implants for load bearing applications. A suitable alloy has to combine highest biocompatibility, an appropriate degradation rate and good mechanical properties, especially a high strength.
The focus of our work is on lean Mg-Zn-Ca alloys which contain only low amounts (<1 wt%) of zinc and calcium, both being essential elements for the human body. Besides an excellent biocompatibility, such alloys also provide a low and controllable degradation rate. To enhance the mechanical properties, Equal Channel Angular Pressing (ECAP) is used in order to produce a homogeneous ultra-fine grained (UFG) microstructure. A double-ECAP tool which was especially designed for the optimization of Mg alloys is applied. Thereby, it is possible to raise the strength of low alloyed Mg to a level which can otherwise be reached by higher alloying only.
This talk will sum up the latest results concerning the mechanical properties as well as the degradation behaviour of low alloyed magnesium. Results from in vitro degradation experiments in simulated body fluid for time periods ranging from a few days up to several weeks are presented. The extensive in vitro characterization is accompanied by preliminary in vivo results of pins implanted in the femoral bones of rats. The characterization of the mechanical properties such as hardness, tensile and compression strength is of particular importance for the further development of biodegradable implants for load bearing applications. The influence of ECAP on mechanical and corrosive properties is discussed as well as its potential for the optimization of Mg alloys.