Shielding AZ91D-1%Ca from corrosion through ultrasound melt treatment: A study for stent design

•Finer β-Mg17Al12 increased corrosion during the first immersion hours.•The ultrasound-treated samples are characterized by uniform corrosion.•Non-treated samples showed severe localized corrosion regions.•Material degradation negatively impacts the mechanical properties of non-treated samples.•Ultrasound treatment can be used to produce Mg-based stents with controlled degradation. Magnesium-based materials show great potential for producing biodegradable stents, but their high corrosion rates are a roadblock. This study investigates whether ultrasound melt treatment can change the corrosion response of an extruded AZ91D-1.0%Ca (wt.%) in Earle's Balanced Salt Solution by tailoring the intermetallics' morphology in the as-extruded state. The results showed that the wires from ultrasound-treated ingots corroded faster than non-treated ones in immersion for up to 6 hours. This trend shifted for longer periods, and ultrasound-treated material showed lower corrosion rates and uniform corrosion, while the non-treated material displayed localized corrosion signs. Tensile testing of the wires demonstrated that immersion in EBSS lowered the tensile strength and elongation at fracture due to material degradation, regardless of the processing route. Nonetheless, this decline was sharper in the non-treated material. These findings suggest that ultrasound melt processing can be a promising method for improving the corrosion resistance of magnesium-based materials, paving the way for their use in manufacturing biodegradable stents.