Effect of extrusion ratio on mechanical and biodegradation behavior of Mg–Zn–Mn–Sr alloy microtubes for biodegradable vascular stents

• Effect of extrusion ratio on Mg-Zn-Mn-Sr (ZMJ100) alloy microtubes was investigated. • Ultra-precise ZMJ100 microtubes were fabricated using a two-step extrusion process. • Higher extrusion ratio enhanced tensile strength via grain boundary strengthening. • Biodegradation rate was directly correlated with grain size and basal texture. This study systematically investigated the influence of the extrusion ratio on the mechanical properties and biodegradation behavior of Mg-Zn-Mn-Sr (ZMJ100) alloy microtubes in relation to their microstructure and texture. The fabrication of ultra-precise ZMJ100 microtubes was successfully achieved through a two-step direct extrusion. As the extrusion ratio increased, the grain refinement and texture weakening played a pivotal role in determining the mechanical and biodegradation behavior. The enhancement of tensile strength was ascribed to grain boundary strengthening due to the higher extrusion ratio, notwithstanding weaker basal texture and higher activation of basal slip. The findings indicated a direct correlation between the biodegradation rate and the inverse square root of grain size, as well as the activation amount of basal slip. An increase in the extrusion ratio led to grain refinement and concurrent texture weakening, accelerating selective grain boundary corrosion and micro-galvanic corrosion between differently oriented grains. It is imperative to meticulously regulate both the grain size and basal texture by calibrating the process parameters, such as the extrusion ratio, to ensure optimal service performance of Mg alloy for bioresorbable stent scaffolds.