Evaluation of material properties and design requirements for biodegradable magnesium stents

Magnesium represents a very attractive material for biodegradable stents since the process of its natural and gradual dissolution into the human body by a corrosion process would prevent restenosis risks and would allow the progressive transmission of the mechanical load to the surrounding tissues after several months of service. The objective of the present work is to develop a frame of mechanical and microstructural data about several commercially available Mg alloys in view of their use for biodegradable stents. The AZ31, AZ61, AZ80, ZM21, ZK61 and WE43 alloys in the form of extruded bars were thus investigated to compare their mechanical properties and corrosion resistance. Further high-temperature characterization was carried out by compression tests at high temperature (temperature range: 260-450°C, strain rate range: 5•10-4 ÷ 3•10-2 s-1) in order to assess the optimal processing window for stent precursors manufacturing (small tubes 1÷2 mm in diameter) by hot extrusion. The experimental results made available by this investigation were adopted to support the development of a finite element (FE) framework combining a shape optimization procedure and a detailed model for Mg alloy mechanical and corrosion damage behavior.