Mechanical performance during corrosion of magnesium alloy wires in artificial urine solution: Insights from an alloy study

Applications of metallic biomaterials such as sutures, knots, coils and certain types of stents require a comprehensive assessment of the resulting property profiles for the intended use case. While the feasibility of wire production and the melting and solidification behavior are a focus for additive manufacturing processing routes, mechanical properties and their development during a degradation period are of primary interest for biomedical applications. The development of distinct mechanical properties of magnesium wires can be controlled by the thermomechanical treatment applied in the manufacturing process and by the alloys used. While the conventional method for wire manufacturing involves drawing processes, direct extrusion using customized dies for enabling envisioned high degrees of deformation allows a single-stage wire production. Depending on the alloy composition different mechanical properties are achieved. This work highlights the potential for controlled development of wires for biomedical applications, demonstrating how various alloy compositions can be optimized to produce wires with the desired properties. While binary Magnesium-Yttrium maintains reasonable mechanical properties and homogeneous degradation profile also during immersion in artificial urine solution, alloys with Calcium as an alloying element revealed increasing brittleness as well as an alloy with sole Indium addition. • Ca results in a strong texture weakening and improvement of formability (wrapping test and knot test) in Mg-Y-Ca and Mg-In-Ca in the as-extruded state. • The four alloys (without I1) have been exposed to AUS for a full 14 days and show rather low corrosion rates well below 0.2 mm/y. • Ca as an additional alloying element shows a marked embrittlement of the wires (tensile test) after exposure to the corrosive environment. • The binary Mg-Y alloy W0 was the only alloy found to retain a comparable property profile after exposure to corrosion.